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Biomedical subjects

M Koivisto

Publications and source records attributed to M Koivisto.

At least 55 records · Page 3Linked to original sources
PubMed1996

Perceptual priming in Alzheimer's and Parkinson's diseases.

The present study focused on perceptual identification priming (implicit memory) in early stages of dementia by studying demographically and cognitively matched patients with Alzheimer's disease (AD) and Parkinson's disease (PD). The AD and PD groups performed normally on perceptual identification priming, whereas their explicit recognition memory was equally impaired compared to normal controls. These results imply that priming in perceptual identification relies on the perceptual memory system which can resist not only impairments of explicit memory but also widespread cognitive deterioration induced by the neurodegenerative processes in AD or PD.

Adolescent↗
PubMed1996

Form-specific priming and functional brain asymmetries in perceptual identification.

Word form representations in intact cerebral hemispheres were studied by a lateralized perceptual identification priming task. During the study phase, word forms were primed by displaying words visually in uppercase or lowercase letters. During the test phase, perceptual identification of non-studied baseline words and studied words (presented in same or different lettercase as studied) was tested by displaying targets in the left or right visual field. Experiment 1 showed that the hemispheric pattern of priming effects was dependent on the lettercase at test. For uppercase test items, only the left visual field/right hemisphere was sentitive to study-test changes in lettercase, replicating an earlier result obtained in word-stem completion (Marsolek, Kosslyn and Squire, 1992). However, lowercase test items did not reveal any asymmetries in the form-dependent priming component indicating that in some conditions form-specific representations are computed in the left hemisphere also. No asymmetries were found in the abstract, form-independent component of priming. Experiment 2 revealed that use of explicit memory in the perceptual identification task eliminated the form-specific priming effects and suggested that the results of Experiment 1 were uncontaminated by explicit memory.

Adult↗
PubMed1995

On functional brain asymmetries in perceptual priming.

Brain asymmetries in implicit memory were studied using a perceptual identification priming paradigm. At the study phase, Subjects rated either the readability or the likeability of words. At the test phase, perceptual priming for these words was measured by presenting stimuli briefly either in the left or in the right visual hemifield. The typeface of the words was varied between the study and test. The orientation task manipulation at the study phase did not influence priming, although it had a powerful effect on a test of explicit memory. Priming effects were form-specific: words which were studied in the same typeface as they were tested were primed more strongly than words which were studied in a different typeface. No hemispheric asymmetries were observed in form-specific priming, but in general, priming was greater in the right hemifield/left hemisphere. These findings suggest that the hemispheres are equally effective in analysing and storing form-specific information at the early stages of word recognition process. Asymmetries favoring the left hemisphere may develop at a higher, more abstract level of presemantic visual word form processing.

Adult↗
PubMed1995

Lateralized free-association priming: implications for the hemispheric organization of semantic memory.

The organization of semantic memory in intact cerebral hemispheres was examined by a free-association priming task. Normal subjects studied a list of word pairs where the semantic relations were either coordinate (e.g. saw-axe) or locative (e.g. bear-forest). Priming of the word pairs was tested by presenting test cues (initial words of the pairs) to the left or to the right visual field. Results showed an interaction between visual field and word pair type, suggesting a qualitative difference in the semantic organization of the hemispheres. Specifically, the results support the view that coordinate relations are represented in both hemispheres whereas locative relations are represented mainly in the right hemisphere.

Brain↗
PubMed1995

Hypercalcemia and nephrocalcinosis in patients with congenital lactase deficiency.

We describe 11 infants with congenital lactase deficiency, whose age at diagnosis varied from 6 to 88 days. At the time of admission, 7 of 10 infants had hypercalcemia. Five of the seven infants for whom renal ultrasonography was performed at the time of diagnosis had medullary nephrocalcinosis. Hypercalcemia ceased within a week of the start of a lactose-free diet. At the time of reevaluation, at the ages of 2 to 10 years, one of the patients still had hypercalciuria and nephrocalcinosis was still present in 3 of 11 patients. The mechanism of hypercalcemia is unclear but may be related to metabolic acidosis or may be promoted by the lactose effect (i.e., by nonhydrolyzed lactose that has a direct enhancing effect on calcium absorption in the ileum).

Acidosis↗
PubMed1995

Radiological incidence and course of bronchopulmonary dysplasia in 100 consecutive low birth weight neonates.

Bronchopulmonary dysplasia (BPD) is an important cause of chronic respiratory distress in low birth infants. The radiological incidence and course of BPD were assessed in 100 consecutive low birth weight infants. Chest radiographs were examined on admission, at the ages of 3 days, 7 days, 2 weeks and 4 weeks and at later follow-up until the examinations were normal. Twelve of the children died. The severity and typical radiological abnormalities of BPD were assessed. Among the children alive, there were 26 with BPD (29.5%). The BPD incidence was highest between the age of 2 weeks and 3 months (18-21%) declining to 3.4% at the age of 12 months. Radiological evidence of BPD was already seen at the age of 2 weeks in 16 of the children. Most cases (73%) had their maximum BPD score at the age of 1 to 3 months. The normalisation of the chest radiography occurred predominantly in the age between 3 and 6 months. The most frequent underlying condition in BPD was hyaline membrane disease in 81%.

Age Distribution↗
PubMed1994

Physiological changes, plasma beta-endorphin and cortisol responses to tracheal intubation in neonates.

Physiological, plasma beta-endorphin and cortisol responses to nasotracheal intubation were studied in 20 distressed infants of median age 0.3 days (range 0.1-23 days) randomized into groups given pethidine 1 mg/kg (n = 10) or alfentanil 20 micrograms/kg plus suxamethonium 1.5 mg/kg (n = 10) before intubation. All of the infants were given glycopyrrolate 3-5 micrograms/kg. Hypoxaemia during intubation was found in all 10 infants in the pethidine group and in 7 of 10 infants in the alfentanil-suxamethonium group, its duration being significantly longer in the pethidine group and being associated with the duration of the intubation procedure. Blood pressure increased, but not statistically significantly, in all except 2 patients in the alfentanil-suxamethonium group and bradycardia appeared in 1 patient in each group. Plasma beta-endorphin and cortisol values did not show any statistically significant intra-group or inter-group differences. Newborn infants suffer from hypoxaemia during intubation when awake more and therefore need adequate premedication before elective intubation. One alternative is the combination of glycopyrrolate, alfentanil and suxamethonium described here, although the ideal medication and dosage still remain to be defined.

Alfentanil↗
PubMed1994

Prenatal dexamethasone treatment in conjunction with rescue therapy of human surfactant: a randomized placebo-controlled multicenter study.

OBJECTIVES: A placebo-controlled, randomized, double-blind study was performed to determine whether prenatal dexamethasone (DEX) treatment improves the outcome of the preterm infant when exogenous surfactant is available. METHODS: 157 pregnant women at five hospitals with threatened preterm delivery and with lengths of gestation < 32 weeks received either DEX (dose 6 mg four times at 12-hour intervals) or placebo (PL). Prenatal treatment was not repeated. Preterm infants received rescue therapy of human surfactant (maximum four doses) if they required ventilatory support and at least 40% oxygen for the treatment of respiratory distress syndrome (RDS). RESULTS: Enrolled pregnant women delivered 188 live-born neonates, of whom 79 (DEX 41 and PL 38 neonates) were born 1 to 14 days after the prenatal treatment. Neonates born within 1 to 14 days after the initial DEX treatment had a lower incidence of RDS (DEX, 44%; PL, 79%; P < .01), lower requirements of surfactant (DEX, 22%; PL, 53%; P < .01), shorter duration of ventilatory support (DEX, 2.0 days; PL, 5.3 days; P < .05) and oxygen therapy (DEX, 2.0 days; PL, 7.0 days; P < .01), and a higher neonatal survival without ventilatory support (P < .05) than PL-treated neonates. DEX-treated neonates had higher mean blood pressure than PL-treated neonates during the first 3 days after birth. Among all neonates treated with DEX, there was a lower incidence of intraventricular hemorrhage or periventricular leucomalacia (DEX, 13%; PL, 33%; P < .01). Reduction in the incidence of intraventricular hemorrhage or periventricular leucomalacia in DEX-treated neonates was particularly associated with exogenous human surfactant therapy (DEX+surfactant 10%; PL+surfactant 48%; P < .01). CONCLUSIONS: Prenatal DEX treatment combined with exogenous human surfactant therapy in preterm infants decreases pulmonary morbidity and cerebral complications, and increases survival without severe morbidity.

Cerebral Hemorrhage↗
PubMed1993

Dexamethasone treatment in preterm infants at risk for bronchopulmonary dysplasia.

A randomised double blind placebo controlled study was conducted to determine whether a one week course of dexamethasone could reduce the severity of bronchopulmonary dysplasia in preterm infants without compromising their adrenal function. Forty one infants with a mean birth weight of 880 g and a gestational age of 27 weeks who were ventilator dependent at 10 days of age were enrolled. At the age of 28 days pulmonary outcome was significantly better in the girls treated with dexamethasone but not in all infants. There was no difference between the groups in the long term outcome, except for a shorter duration of supplemental oxygen in dexamethasone treated female infants. After the one week dexamethasone treatment there was a significant but short lived suppression of the basal cortisol concentrations and the adrenal response to corticotrophin (ACTH). No serious side effects were observed. It is concluded that early one week dexamethasone treatment improves short term pulmonary outcome in premature infants, but there is no clear evidence of long term benefits.

Bronchopulmonary Dysplasia↗
PubMed1993

Age-related morphine kinetics in infants.

The pharmacokinetics of morphine was studied in 27 infants receiving a single intravenous dose of 0.1 mg/kg morphine after surgery (n = 23) or during mechanical ventilation (n = 4). The pharmacokinetics of morphine varied greatly between the subjects, especially in the neonates. The clearance and half-life varied distinctly with postnatal age. The mean (+/- SD) half-life was 8.1 +/- 8.1 h in 10 neonates younger than 1 week, 5.4 +/- 3.4 h in 10 infants aged from 1 week to 2 months and 2.6 +/- 1.7 h in 7 infants aged from 2 to 6 months. Mean clearance increased significantly with age, being 8.7 +/- 5.8 ml/min/kg in the youngest age group, 11.9 +/- 5.1 ml/min/kg in those aged 1 week to 2 months and 28.0 +/- 8.9 ml/min/kg in those aged 2-6 months, and was also significantly lower in the critically ill infants. The clearance and half-life of morphine begin to approach adult values after the age of 1 month, but great individual variability exists even after that. In order to reduce the risk of overdosing or underdosing, the dose of morphine should be titrated individually.

Aging↗
PubMed1993

Hormonal enteroinsular axis in newborn infants of insulin-treated diabetic mothers.

To study whether the increased glucose levels in the amniotic fluid during diabetic pregnancies induce an early maturation of the hormonal enteroinsular axis, we measured blood glucose levels and plasma concentrations of C-peptide, pancreatic glucagon, enteroglucagon, and gastric inhibitory polypeptide (GIP) in cord blood from 18 newborn infants of insulin-treated diabetic mothers (IDM) and 18 infants of nondiabetic mothers. In addition, we studied the same parameters in 20 IDM and 12 control infants before and after their first feed comprising human milk (5 mL/kg), given by nasogastric tube at the age of 2 h. The IDM had significantly higher blood glucose levels and plasma C-peptide concentrations in their cord blood than the control infants, which was followed postnatally by a substantial fall in these levels, whereas a more modest decrease could be seen in the control infants. Circulating enteroglucagon and GIP concentrations at the age of 2 h were significantly higher than those observed in cord blood in both the IDM and the control infants, but the IDM had significantly lower blood glucose levels, higher plasma C-peptide, and lower enteroglucagon concentrations before the first feed. There was a significant increase in blood glucose levels after the feed in both the IDM and the control infants, and the concentrations 2 h after feeding were of the same magnitude in the two groups. No significant C-peptide response could be observed in either group, but the IDM continuously had higher C-peptide concentrations. A significant enteroglucagon and GIP response could be seen in the IDM, whereas the controls exhibited only a GIP response. However, no significant differences were found between the two groups in the absolute postprandial plasma concentrations of these hormones. Our results show rapid, substantial postnatal changes in circulating concentrations of enteroinsular hormones in both IDM and control infants. Enteral feeding with human milk corrects early postnatal hypoglycemia within 2 h in most IDM without causing any exacerbation of their hyperinsulinemia. The absence of any C-peptide response to the first feed and of any observed differences between IDM and normal infants in absolute concentrations of enteroglucagon and GIP after the first feed suggests that the enteroinsular axis matures postnatally in both groups of infants.

Blood Glucose↗
PubMed1992

Pharmacokinetics and pharmacodynamics of intravenous meperidine in neonates and infants.

The pharmacokinetics of meperidine (pethidine) was studied in 21 infants who received a single intravenous dose of 1 mg/kg after surgery (n = 18) or during mechanical ventilation because of respiratory distress (n = 3). Eleven patients were younger than 1 week old, 10 patients were aged from 3 weeks to 5 months, and five of the patients were premature. The pharmacokinetics of meperidine varied greatly between the subjects, with a median elimination half-life of 10.7 hours (range, 3.3 to 59.4 hours), median clearance of 8.0 ml/kg/min (range, 1.8 to 34.9 ml/kg/min), median volume of the central compartment of 2.4 L/kg (range, 0.5 to 4.8 L/kg), and median steady-state volume of distribution 7.2 L/kg (range, 3.3 to 11.0). The great interindividual variability in meperidine pharmacokinetics should be taken into consideration when meperidine is administered to neonates. Although no life-threatening or serious side effects were observed in this study, appropriate care should be exercised when prescribing meperidine for this age group.

Aging↗
PubMed1992

Splenic abscess. Imaging and intervention.

We reviewed the imaging findings of 14 splenic abscesses in 13 patients. All patients underwent chest radiography, 12 ultrasonography (US), 9 CT, 4 plain abdominal radiography, 2 99mTc-HMPAO leukocyte scan and 2 99mTc-HIG scan. Three patients were treated with percutaneous catheter drainage, and 5 with diagnostic or therapeutic fine-needle aspiration (FNA). At US the abscess was hypoechoic (n = 9), anechoic (n = 2), or anechoic with gas-bubbles (n = 1), or the entire spleen was inhomogeneous with gas-bubbles (n = 1). At CT the abscesses appeared as low density (18-30 HU) lesions with (n = 2) or without (n = 7) gas. In 2 cases 99mTc-HMPAO leukocyte scan, and in one case 99mTc-HIG scan showed an intrasplenic defect, and in one case 99mTc-HIG scan was considered normal. At plain abdominal radiography extraintestinal gas was suggested in 2 patients, and the findings were normal in 2. US-guided FNA confirmed infectious etiology of the lesion in 4 patients, and a necrotic specimen suggested infection in one. One patient was cured with repeated aspirations. Catheter drainage was successful in all 3 patients who underwent the procedure. We conclude that US and CT are accurate in detecting splenic abscesses. Our results in splenic interventions advocate wider use of the procedures.

Abscess↗
PubMed1989

Circulating sex hormone-binding globulin and testosterone in newborns and infants.

The concentrations of sex hormone-binding globulin (SHBG) and testosterone (T) were measured in the cord blood of full-term newborns (14 boys, 15 girls) and pre-term newborns (10 boys, 5 girls), and in the venous circulation of 100 full-term infants aged 1-204 days. The ratio of T to SHBG (the 'free androgen index', FAI) was calculated to reflect the level of unbound T (the free, biologically active fraction). In boys' umbilical cord sera, T concentrations were significantly greater in arterial than in venous sera, while there was no such difference in the concentration of SHBG. Levels of SHBG in cord sera were considerably lower than those seen in the maternal circulation at term, but they were significantly greater in boys' than in girls' cord sera. Levels of T, and the FAI, were significantly greater in boys' arterial cord sera than in girls'. In early infancy, SHBG concentrations rose in both sexes, the highest values being seen in girls. In infant girls, levels of T and the FAI were constantly low. In infant boys, the expected peak in serum T concentrations was observed at 1-3 months the values approaching those seen in men. In contrast, values of the FAI at this age were relatively low, similar to those seen in women. This suggests that the elevation of male serum T during the first months of life lacks biological significance. However, it is important to realise that the FAI in male infants is about one order of magnitude larger than that in female infants at this time.

Androgens↗
PubMed1989

Comparison of the effects of general and epidural anaesthesia for caesarean section on the neurobehavioural responses of newborn infants.

Thirty-one neonates delivered by elective caesarean section were evaluated at the ages of 3 h, 1 day, 2 days and 4-5 days using Scanlon's Early Neonatal Neurobehavioural Scale and tests for orientation. Thirteen of the mothers received general anaesthesia and 18 epidural anaesthesia. All the mothers were healthy and not in labour. All the neonates weighed 2500 g or more and had Apgar scores of 7 or more at 1, 5 and 15 min. The neonates delivered with epidural anaesthesia scored significantly lower on rooting at the age of 3 h than those delivered with general anaesthesia, but the latter scored significantly lower on habituation to sound and orientation to both animate and inanimate visual stimuli. General anaesthesia seemed to depress the infants' interactive processes (orientation items), and their ability to make an appropriate response to repetitive stimuli (habituation) more than did epidural anaesthesia, indicating greater global depression. This depression was short-lived, however, and there were no differences between the groups on any of the parameters after 24 h.

Adult↗
PubMed1989

Neonatal septicaemia in Finland 1981-85. Predominance of group B streptococcal infections with very early onset.

A survey of blood culture-confirmed neonatal septicaemia was carried out in seven delivery hospitals in 1981-85, for a second successive five-year period. The total number of cases was 377, to compare with 410 in the previous five-year period. Group B streptococcus (GBS) was throughout the major pathogen (29%), followed by Staphylococcus aureus (15%) and Escherichia coli (14%), while Staphylococcus epidermidis (10%) has emerged as a significant new causative agent. Septicaemia with very early onset was predominant: 49% of the cases had onset within the first 24 hours; in the majority the symptoms were present from birth. GBS was responsible for 49% of the cases detected in the first 24 hours of life. The overall mortality was 20% as compared to 23% in the previous five-year period, whereas in the very early onset septicaemia mortality was now 18%, down from the preceding 30%. Despite the modest progress, GBS septicaemia with very early onset remains a significant problem, and effective preventive measures are needed.

Finland↗