Yukuo Konishi

A rapid brain metabolic change in infants detected by fMRI

TO determine developmental changes of activity-related metabolism in human visual cortex, we performed functional magnetic resonance imaging (fMRI) from the neonatal period. A rapid metabolic changing pattern accompanying normal human brain maturation was revealed by fMRI with photic stimulation. Infants older than 8 weeks of age showed a stimulus-related signal decrease in the visual cortex, whereas younger neonates showed a signal increase. This inversion of response in infants suggests a change in oxygen consumption during neuronal activation, which is related to rapid synapse formation and accompanying increased metabolism. fMRI can detect dynamic metabolic changes during the brain maturation, and provides a new clue in the detection of abnormal brain development or CNS plasticity.

A milestone for normal development of the infantile brain detected by functional MRI

Objective: To investigate the relationship between cerebral cortical function and white matter myelination in the visual pathway in the evaluation of normal brain development. Methods: The authors performed quantitative analysis of white matter myelination detected with conventional T1-weighted spin echo (SE) MRI and brain functional MRI (fMRI) using echoplanar imaging with photic stimulation in 27 neurologically normal infants (age range, 0 to 22 weeks). Results: An age-dependent gradual increase in signal intensity was observed in optic radiation on the T1-weighted SE images, indicating progression of white matter myelination. A rapid age-dependent reverse in signal response was observed on fMRI. Infants older than 8 weeks showed a stimulus-induced signal decrease in the visual cortex, whereas infants younger than 7 weeks showed a signal increase. Conclusions: A rapid inversion of response revealed by fMRI with photic stimulation in infants suggests a change in oxygen consumption during neuronal activation, which is related to rapid synapse formation and accompanying increased metabolism. fMRI can detect dynamic metabolic changes during brain maturation, which is a different developmental process from white matter myelination. The metabolic changes detected by fMRI provide a milestone for the evaluation of normal brain development.

Age-dependent change in metabolic response to photic stimulation of the primary visual cortex in infants: functional magnetic resonance imaging study.

The blood oxygen level-dependent (BOLD) response to photic stimulation in the primary visual cortex (V1) reverses from positive to negative around 8 weeks of age. This phenomenon may be caused by increased oxygen consumption during stimulation as the result of a rapid increase of synaptic density at this age. To test this hypothesis, we applied existing mathematic models of BOLD signals to the experimental data from infants. When the stimulus-related increments of cerebral blood flow and cerebral blood volume were fixed at 60% and 20%, respectively, the mean estimated increment of the cerebral metabolic rate of oxygen of the V1 in the elder infant group (57.1% ± 8.8%) was twice as large as that in the younger infant group (32.2% ± 4.7%), which corresponds to the reported difference in synaptic density. The present data confirmed that a change in oxygen consumption could explain a transition from a positive to a negative BOLD response.

Bone Mineral Status in Preterm-Born Children: Assessment by Dual-Energy X-Ray Absorptiometry

To elucidate the long-term consequences of osteopenia of prematurity, lumbar spinal bone mass was measured in 21 preterm-born children aged 3-4 years by dual-energy X-ray absorptiometry. Their mineral intake remained low during early life, and all 11 infants previously studied were osteopenic at term postconception. At the age of 3-4 years, however, all 21 children were found to have normal bone mineral content and density with slightly elevated serum osteocalcin levels. Our results show that in preterm-born children spontaneous resolution of lumbar spinal osteopenia occurs during early childhood.

Use of ultrasonography in the detection of ureteric reflux in children suspected of having urinary infection

The present study investigated whether ultrasonography was effective in detecting ureteric reflux in children suspected of having urinary infection. Seventeen children with febrile episodes and pyuria were enrolled. The ultrasound examination revealed ballooning of the renal pelvis during bladder contraction in 4 children, dilatation of the distal ureters in 6, and small kidney in 2. Cystography was performed on the 6 children with these ultrasound abnormalities and 1 child with two episodes of suspected urinary infection. Four children showed reflux. All of the 4 children had been found to have renal pelvic ballooning on ultrasound. None of the children who did not undergo cystography had recurrence of urinary infection or significant bacteriuria during a median follow‐up period of 12 months. Thus, scanning during bladder contraction was effective in detecting significant ureteric reflux.

Urinary uric acid excretion in term and premature infants

Objective: To clarify postnatal changes in urinary uric acid (UA) excretion in normal term infants and to examine the effects of prematurity or illness on the UA excretion.

Ultrasonography for the detection of ureteric reflux in infants with urinary infection

Several less harmful methods than voiding cysto‐urethrography for detecting significant ureteric reflux have been proposed. The present prospective study investigated whether ultrasonography was effective in identifying ureteric reflux in infants with their first febrile urinary infection. The subjects were 27 infants (24 boys and 3 girls) aged from 0 to 8 months. The urinary tract was scanned when the bladder was full, and before and during induced voiding. Infants with abnormal ultrasound findings underwent voiding cysto‐urethrography. The other infants were followed and those who had a recurrence of urinary infection underwent voiding cystography.

Urinary Selenium Excretion in Infancy: Comparison between Term and Preterm Infants

We evaluated the urinary excretion of selenium (Se), an essential component of glutathione peroxidase, in infants aged 1 week and 1, 4, and 7 months and examined the relationship between urinary Se and renal function. Daytime spot urine samples from a total of 80 infants were analyzed. The Se concentration in urine was measured by fluorometry, while the beta 2-microglobulin content, an index of renal tubular function, was determined by radioimmunoassay. In healthy term infants, the urinary Se excretion showed a peak level at 1 month of age. In contrast, the urinary Se concentration rapidly decreased in preterm infants from 1 week to 7 months postnatally. The level at 1 week in preterm infants was significantly higher than that in term infants, although the mean levels at 1, 4, and 7 months were lower in preterm infants. The level of urinary Se did not correlate significantly with the beta 2-micro-globulin concentration, either in term or preterm infants at any age investigated. Our results suggest that the renal excretion of Se probably reflects the body stores of Se and is not related directly to the renal function in infants. Urinary Se, a noninvasive marker of the Se status, may be used for diagnosis and follow-up of Se deficiency in infants.