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Biomedical subjects

M Koivisto

Publications and source records attributed to M Koivisto.

At least 19 recordsLinked to original sources
PubMed2004

Changing incidence and outcome of infants with respiratory distress syndrome in the 1990s: a population-based survey.

AIM: To evaluate the trends in the incidence, clinical course and outcome of respiratory distress syndrome (RDS) in the newborn in the Oulu University Hospital region in northern Finland. METHODS: In the population of 58 990 infants, the incidence rates of RDS specific to gestational age and birthweight in two consecutive periods, 1990-95 and 1996-99, were calculated. Clinical course and other neonatal morbidities were reported. All surviving infants were followed up until 1 y of corrected age. RESULTS: The overall incidence of RDS did not change significantly (8.7/1000 livebirths in 1990-95 vs 7.6 in 1996-99; p = 0.15), but the gestational age-adjusted incidence decreased between the two consecutive periods (p = 0.005). The frequency of infants with gestational age below 28 wk tended to increase towards the late 1990s, while their RDS incidence remained unchanged. RDS-related neonatal mortality decreased in parallel with neonatal mortality, accounting for 15% of all neonatal deaths. The duration of oxygen therapy shortened (8.0 vs 5.5 d) and the incidence of pneumothorax decreased (9.7 vs 4.1%), whereas the rate of chronic lung disease at 36 wk of postconceptional age (16.4 vs 16.7%) and at 1 y of corrected age (9.2 vs 8.2%) remained unchanged, as did also associated neurosensory morbidity (8.8 vs 9.5%). CONCLUSION: During the 1990s, the incidence of RDS shifted towards more immature infants and the gestational-age specific incidence decreased. The course of the disease shortened and acute complications decreased. The frequency of chronic pulmonary sequelae (and associated neurosensory morbidity) at the age of 1 y did not change significantly.

Adult↗
PubMed2003

Minimum description length block finder, a method to identify haplotype blocks and to compare the strength of block boundaries.

We describe a new probabilistic method for finding haplotype blocks that is based on the use of the minimum description length (MDL) principle. We give a rigorous definition of the quality of a segmentation of a genomic region into blocks and describe a dynamic programming algorithm for finding the optimal segmentation with respect to this measure. We also describe a method for finding the probability of a block boundary for each pair of adjacent markers: this gives a tool for evaluating the significance of each block boundary. We have applied the method to the published data of Daly and colleagues. The results expose some problems that exist in the current methods for the evaluation of the significance of predicted block boundaries. Our method, MDL block finder, can be used to compare block borders in different sample sets, and we demonstrate this by applying the MDL-based method to define the block structure in chromosomes from population isolates.

Haplotypes↗
PubMed2003

Effects of short-term dexamethasone treatment on collagen synthesis and degradation markers in preterm infants with developing lung disease.

AIM: To assess the effects of dexamethasone treatment on collagen turnover in preterm infants. METHODS: The serum concentrations of the amino-terminal propeptide of type I and III procollagens (PINP and PIIINP), which reflect rates of type I and III collagen synthesis, respectively, and the carboxy-terminal telopeptide of type I procollagen (ICTP), which reflects the rate of type I collagen degradation, were monitored in 13 preterm infants receiving dexamethasone and 13 matched control infants without glucocorticoid treatment for a total period of 12 mo. Dexamethasone was started at a median age of 12 d and continued at tapering doses for a median total duration of 10 d. Blood samples were taken immediately after birth, at 7, 14 and 28 d of age and at 2, 3, 6, 9 and 12 mo. The same markers were also measured just before the initiation of dexamethasone and on days 1, 3, and 7 of treatment. RESULTS: A striking decrease in all of the markers was already observed in every case on day 1 of dexamethasone, the suppression being greatest on day 3 and still considerable on day 7. The percentages from the pretreatment levels recorded on days 1, 3 and 7 were: for PINP 51, 26 and 45%; for PIIINP 63, 44% and 52%; and for ICTP 64, 41 and 51%. A rebound rise in PINP levels was seen in dexamethasone-treated infants, the levels exceeding those of the controls at 3 and 6 mo of age. A similar phenomenon was noted concerning PIIINP at 3 mo. The levels settled down at 9 and 12 mo. CONCLUSION: Dexamethasone causes an immediate, inevitable, deep suppression of type I and III collagen synthesis and also type I collagen degradation. This should be taken into consideration, e.g. when assessing for the indications for steroid treatment in sick preterm infants and its dosing and duration.

Anti-Inflammatory Agents↗
PubMed2003

An MDL method for finding haplotype blocks and for estimating the strength of haplotype block boundaries.

We describe a new method for finding haplotype blocks based on the use of the minimum description length principle. We give a rigorous definition of the quality of a segmentation of a genomic region into blocks, and describe a dynamic programming algorithm for finding the optimal segmentation with respect to this measure. We also describe a method for finding the probability of a block boundary for each pair of adjacent markers: this gives a tool for evaluating the significance of each block boundary. We have applied the method to the published data of Daly et al. The results are in relatively good agreement with the published results, but also show clear differences in the predicted block boundaries and their strengths. We also give results on the block structure in population isolates.

Algorithms↗
PubMed2002

HRCT findings in the lungs of primary care patients with lower respiratory tract infection.

PURPOSE: To survey the prevalence and type of lung patterns detectable at high-resolution CT (HRCT) in a primary care population seeking help for cough and fever. MATERIAL AND METHODS: The HRCT patterns of 103 patients obtained at the primary visit to a municipal health centre for cough and fever were evaluated. Forced expiratory examinations were obtained in 93 patients. RESULTS: Lower respiratory tract infection (LRTI)-related findings (present at inclusion, healed at follow-up, not explained by any other factor) were seen in 19 patients (18.7%), of whom 11 also showed opacities, even though of lesser extent, at conventional chest radiography. The following patterns were found: ground-glass opacity (58%), discrete consolidations (52%), confluent consolidations (16%; 1 case with an air bronchogram), air space nodules (10%), peribronchovascular thickening (37%), tree-in-bud pattern (26%), free pleural fluid (5%), and septal thickening (5%). An expiratory mosaic pattern was seen in 19 (20%) out of 93 patients. In addition, lymph node enlargement (>1 cm) was recorded in 7 patients out of 103. CONCLUSION: HRCT is more sensitive than chest radiography in detecting LRTI-related lung lesions in a primary care population. The pattern typically comprises subtle scattered polymorphous opacities with varying attenuation affecting several lung segments. LRTI-related HRCT pattern deserves consideration as a differential diagnostic alternative in patients examined due to any lower respiratory tract symptoms.

Adult↗
PubMed2001

GSM phone signal does not produce subjective symptoms.

The influence of pulsed radiofrequency (RF) electromagnetic fields of digital GSM mobile phones (902 MHz, 217 Hz pulse modulation) on subjective symptoms or sensations in healthy subjects were studied in two single-blind experiments. The duration of the RF exposure was about 60 min in Experiment 1 and 30 min in Experiment 2. Each subject rated symptoms or sensations in the beginning of the experimental session and at the end of both the exposure and the nonexposure conditions. The symptoms rated were headache, dizziness, fatigue, itching or tingling of the skin, redness on the skin, and sensations of warmth on the skin. The results did not reveal any differences between exposure and non-exposure conditions, suggesting that a 30-60 min exposure to this RF field does not produce subjective symptoms in humans.

Adolescent↗
PubMed2001

Cognitive representations underlying the N400 priming effect.

The present study explored whether the N400 semantic priming effect is based on semantic similarity or lexical associations, or both. The event-related potentials showed N400 priming effects for both semantically similar and lexically associated word pairs in the 250-375 ms time-window. However, the effect lasted for a longer time for lexical associates, particularly in frontal and central electrode sites in the 375-500 ms time-window, suggesting that different types of processing may contribute to the N400 priming effects evoked by the two types of relationships.

Adult↗
PubMed2001

Type I collagen markers in cord serum of appropriate vs. small for gestational age infants born during the second half of pregnancy.

BACKGROUND: The serum concentration of the N-terminal propeptide of type I procollagen (PINP) reflects the synthesis rate of type I collagen, whereas the corresponding C-terminal telopeptide (ICTP) mirrors its degradation. DESIGN: PINP and ICTP were measured in a total of 690 cord serum samples from 592 appropriate-for-gestational-age (AGA) infants and 98 smal-for-gestational-age (SGA) infants. These markers were compared between AGA and SGA infants of different gestational ages, ranging from 23 to 41 weeks, and birth weights, from 620 to 4555 g. RESULTS: Both PINP and ICTP levels were very high in the preterm AGA infants and declined significantly with advancing gestational age, paralleling the shape of the fetal growth velocity curve. Regardless of the quite large interindividual variations observed in these markers, PINP was significantly lower in both the preterm and term AGA infants than in the SGA infants. This was also the case for ICTP in the preterm infants of gestational age less than 36 weeks. In stepwise multiple regression analyses, gestational age, being either AGA or SGA and head circumference were significant factors to explain the levels of PINP and ICTP. The levels of PINP and ICTP were correlated with each other highly significantly in both the AGA and SGA infants (rs = 0.700 and 0.692, respectively; P < 0.001 in both). CONCLUSIONS: The levels of type I collagen markers seem to follow closely the shape of the fetal growth velocity curve during different stages of gestation. However, because of the large interindividual variations observed, further studies are needed before the significance of these markers for the assessment of normal and abnormal fetal growth can be established.

Biomarkers↗
PubMed2001

Brain single photon emission computed tomography at term age for predicting cerebral palsy after preterm birth.

In order to assess the predictive value of neonatal brain perfusion with single photon emission computed tomography (SPET) with regard to neuromotor outcome at a corrected age of 18 months, 34 infants with birth weight <1,500 g and gestation age <34 weeks underwent brain technetium-99m ethylcysteinate dimer (99Tc(m)-ECD) SPET at term age. The perfusion defects were estimated by visual interpretation. Consecutive semiquantitative assessment was made in 26 cases and reference values for the tracer were collected from images of 17 preterm infants with normal outcome after the follow-up period. Relative regional cortical (frontal, sensorimotor, parietal and occipital), cerebellar and thalamic perfusion levels were evaluated in middle sagittal slices and hemispheric asymmetries in transaxial slices. Perfusion defects predicted cerebral palsy (CP) (n = 11) with 82% sensitivity, 70% specificity and 74% accuracy, the corresponding figures for ultrasound (US) being 73, 83 and 79%, respectively. The sensitivity of SPET in predicting moderate or severe CP (n = 7) was 100% and the specificity 67%, the corresponding figures for US being 71% and 74%, respectively. Brain SPET seems to identify the most severe forms of CP in preterm infants very well at term age, but cannot identify all mild ones. In addition to a low specificity, the radiation exposure restricts usefulness of the method for clinical purposes.

Aging↗
PubMed2001

Offspring risk and sibling risk for multilocus traits.

The recurrence risk of a trait in a relative of type R is the probability that an individual who is in relationship of type R to an affected proband has the trait. It is intuitively clear that closer relationships lead to higher recurrence risks. However, no exact analysis of this phenomenon has been presented for multilocus traits. We prove a theorem that shows how recurrence risks are influenced by the degree of closeness of the relationship R. For example, our theorem implies that sibling risk is always higher than offspring risk. The loci influencing the trait are assumed to be autosomal and unlinked, but arbitrary epistasis between the loci is allowed. We give a detailed proof of the theorem by using stochastic matrices. A shorter proof based on the additive and dominance genetic variances is also sketched. Additionally, we also give some empirical results and discuss generalizations of the theorem.

Chromosome Mapping↗
PubMed2001

Effect of short-term antenatal dexamethasone administration on type I collagen synthesis and degradation in preterm infants at birth.

UNLABELLED: To assess the effects of antenatal corticoid administration on foetal collagen metabolism, cord serum concentrations of the aminoterminal propeptide and carboxyterminal telopeptide of type I procollagen (PINP and ICTP), which reflect rates of type I collagen synthesis and degradation, respectively, were measured in 67 consecutive preterm infants with gestational ages ranging from 24 to 32 wk. The samples were divided into three groups, depending on the administration and timing of antenatal corticosteroid treatment for enhancement of foetal lung maturity: cases in which the mothers had received a full 2-dose administration of dexamethasone on consecutive days 1 to 6 d before delivery (n = 23; Complete-Dexa), those who had received only a single dose of dexamethasone less than 24 h before delivery (n = 17; Partial-Dexa) and those who had not received any antenatal steroids (n = 27; No-Dexa). Infants in the Complete-Dexa group had significantly lower median PINP levels than those in the No-Dexa group (3,326 vs 4,028 microg/l; p = 0.036); the median PINP level in the Partial-Dexa group (3,999 microg/l) was close to that of the No-Dexa group. No significant differences in ICTP concentrations were seen between the groups. CONCLUSION: A significant suppression of foetal collagen synthesis but not degradation was found to be associated with antenatal dexamethasone administration. This should be taken into consideration, e.g. when assessing whether to administer repeated or single courses of corticosteroids antenatally in high-risk pregnancies.

Anti-Inflammatory Agents↗
PubMed2000

The effects of electromagnetic field emitted by GSM phones on working memory.

The influence of pulsed radiofrequency (RF) electromagnetic fields of digital GSM mobile phones on working memory in healthy subjects were studied. Memory load was varied from 0 to 3 items in an n-back task. Each subject was tested twice within a single session, with and without the RF exposure (902MHz, 217Hz). The RF field speeded up response times when the memory load was three items but no effects of RF were observed with lower loads. The results suggest that RF fields have a measurable effect on human cognitive performance and encourage further studies on the interactions of RF fields with brain function.

Adolescent↗
PubMed2000

Effects of electromagnetic field emitted by cellular phones on the EEG during a memory task.

The effects of electromagnetic fields (EMF) emitted by cellular phones on the ERD/ERS of the 4-6 Hz, 6-8 Hz, 8-10 Hz and 10-12 Hz EEG frequency bands were studied in 16 normal subjects performing an auditory memory task. All subjects performed the memory task both with and without exposure to a digital 902 MHz EMF in counterbalanced order. The exposure to EMF significantly increased EEG power in the 8-10 Hz frequency band only. Nonetheless, the presence of EMF altered the ERD/ERS responses in all studied frequency bands as a function of time and memory task (encoding vs retrieval). Our results suggest that the exposure to EMF does not alter the resting EEG per se but modifies the brain responses significantly during a memory task.

Adult↗
PubMed2000

Effects of 902 MHz electromagnetic field emitted by cellular telephones on response times in humans.

The present study examined possible influences of a 902 MHz electromagnetic field emitted by cellular telephones on cognitive functioning in 48 healthy humans. A battery of 12 reaction time tasks was performed twice by each participant in a counterbalanced order: once with and once without the exposure to the field. The results showed that the exposure to the electromagnetic field speeded up response times in simple reaction time and vigilance tasks and that the cognitive time needed in a mental arithmetics task was decreased. The results suggest that exposure to the electromagnetic field emitted by cellular telephones may have a facilitatory effect on brain functioning, especially in tasks requiring attention and manipulation of information in working memory.

Adolescent↗
PubMed2000

Factors predicting peri- and neonatal outcome in diabetic pregnancy.

A population-based birth cohort including 296 consecutive type 1 diabetic births in a geographically defined catchment area was used to evaluate factors predicting poor perinatal and neonatal outcome. Though perinatal mortality has decreased (17.1/1000 births at 28 or more weeks of gestation), the neonatal morbidity rate still remains high despite improved maternal metabolic control and developed antepartum surveillance. Poor glycemic control during the first weeks of pregnancy was the most important risk factor (relative risk (RR) 2.91; 95% confidence interval (CI) 1.29-6.55) predicting adverse neonatal events such as long (>10 days) stay in the neonatal unit, malformation or perinatal death. The risk was further increased in cases of severe diabetes (White class F-R; RR 2.75; 95% CI 1.59-4.76) and primiparity (RR 1.64; 95% CI 1.02-2.65). By evaluating these risk factors at the first antenatal visit, a subgroup with a particular need of counselling and intensive feto-maternal monitoring can be identified.

Adult↗
PubMed2000

Semantic priming by pictures and words in the cerebral hemispheres.

In order to determine whether pictures would act as more effective semantic primes than words in the right cerebral hemisphere, automatic semantic activation in intact hemispheres was studied with primed GO-NOGO lexical decision tasks by presenting word-word and picture-word pairs to the left visual field (right hemisphere) or to the right visual field (left hemisphere). Response times in Experiment 1 showed that categorically related targets (e.g., TABLE-BED) were primed only in the right visual field after both word and picture primes. Experiment 2 found that picture primes activated the representations of the corresponding written names in both visual fields. These observations suggest that the range of automatic semantic activation is larger in the left than in the right hemisphere. The results implicate that semantic categories may be organized in a different fashion in the left than the right hemisphere.

Adult↗
PubMed2000

Interhemispheric interaction in semantic categorization of pictures.

Interhemispheric processing may either increase or decrease the processing power of the brain. The two experiments presented here examined in normal subjects whether hemispheric interaction would be useful or not in semantic categorization of pictures. It was tested whether the advantages of dividing the processing between the hemispheres would increase when the experimental task was kept constant but the computational demands of the stimuli was increased. The critical stimuli were either identical (two copies of the same picture) or semantically related pictures (e.g., apple-banana). The stimuli were presented either unilaterally to the same hemisphere or bilaterally to the opposite hemispheres. The results from the two experiments showed a bilateral advantage in categorization of the semantically related pictures but not in categorization of the less demanding identical pictures. The results support the hypothesis that the cognitive capacity of the brain can be increased by dividing the processing of relatively demanding stimuli between the hemispheres.

Adult↗