Functional magnetic resonance imaging in pediatrics

Functional magnetic resonance imaging (fMRI) allows non-invasive assessment of human brain function in vivo by detecting blood flow differences. In this review, we want to illustrate the background and different aspects of performing functional magnetic resonance imaging (fMRI) in the pediatric age group. An overview over current and future applications of fMRI will be given, and typical problems, pitfalls, and benefits of doing fMRI in the pediatric age group are discussed. We conclude that fMRI can successfully be applied in children and holds great promise for both research and clinical purposes.

Language processing during natural sleep in a 6-year-old boy, as assessed with functional MR imaging

Functional MR imaging for language lateralization was performed in a 6-year-old child before neurosurgical intervention. A passive story-listening task was used; this revealed a bilateral language network. The task was repeated during the same session when the child had fallen asleep and surprisingly yielded strong activation in similar language areas. Our findings suggest that language processing does occur during natural sleep, even in young children. This potentially allows for an assessment of language functions, even in sleeping children.

Assessment of spatial normalization of whole-brain magnetic resonance images in children

Commonly used frameworks for spatial normalization of brain imaging data (e.g., Talairach-space) are based on one or more adult brains. As pediatric brains are different in size and shape from adult brains and continue to develop through childhood, we aimed to assess the influence of age on various spatial normalization parameters. One hundred forty-eight healthy children aged 5-18 years were included in this study. The linear scaling parameters and the deformations from the non-linear spatial normalization to both a standard adult and a custom pediatric template were analyzed within SPM99. The effect of using a brain mask on the linear and of using different levels of constraint on the non-linear spatial normalization was assessed. Of the linear scaling factors, only the X-dimension (left-right) showed a significant age-correlation when based on brain tissue, whereas the overall scaling was not correlated with age. When based on the whole head, a very strong age-effect can be found in all dimensions. Non-linear deformations also show localized correlations with age, most pronounced in parietal and frontal areas. The total amount of volume change is significantly lower when using a pediatric template. It is also substantially influenced by the degree of regularization that is exerted on the spatial normalization parameters. Our results suggest that in the cortical areas showing a strong correlation of deformation with age, caution should be used in assigning imaging results in children to a specific morphological structure. Also, to minimize the amount of deformation during non-linear spatial normalization, a pediatric template should be used. Further implications of our findings on developmental neuroimaging studies are discussed.

Allele specific PCR for the minor Histocompatibility antigen HA-2

The hematopoietic system restricted minor Histocompatibility antigen (mHag), HA-2, is encoded by the novel human class I Myosin gene, MYO1G, located on the short arm of chromosome 7. The HA-2 encoding region is di-allelic and comprises the HLA-A2 restricted T cell epitope YIGEVLVSV (HA-2V) and its allelic counterpart YIGEVLVSM (HA-2M). We designed a sequence specific PCR (SSP) for both HA-2 alleles. The HA-2 genomic typing results were compared with the HA-2 CTL phenotyping in three families and revealed exact correlation. The mHag HA-2 SSP can be incorporated in DNA based typing protocols.

Differences in white matter architecture between musicians and non-musicians: a diffusion tensor imaging study

Previous studies found structural brain differences between musicians and non-musicians. In order to determine possible differences in white matter architecture, diffusion tensor imaging was performed on five adult subjects with musical training since early childhood, and seven adult controls. The musicians displayed significantly greater fractional anisotropy (FA) in the genu of the corpus callosum, while significantly less FA was found in the corona radiata and the internal capsule bilaterally. Further areas also showed significant differences. We hypothesize that these changes are due to the cognitive and motor effects, respectively, of musical training.

Development of a technique for transcervical collection of uterine tissue in bitches

Transcervical collection of endometrial tissue specimens is a valuable and well established tool for the diagnosis of reproductive disorders in cows, mares and women, but it is not used currently in bitches. Endometrial biopsy samples were collected by transcervical cannulation from the cranial uterine body at defined stages of the oestrous cycle using biopsy forceps. In study 1, the histology of 45 biopsy specimens taken from 23 Beagle bitches were compared with larger tissue samples collected post mortem. For further evaluation of representative biopsy specimens, the expression of oestrogen and progesterone receptors was determined. Only 31.1% of the biopsy samples taken from bitches could be evaluated and they showed stroma, capillaries, luminal epithelium, glandular ducts and apical glands; however, basal glands and myometrium were not observed. Biopsy findings were in agreement with the diagnosis of the uterine specimens concerning endometrial differentiation, inflammatory and degenerative lesions. The expression of oestrogen and progesterone receptors was slightly lower in the biopsy samples. In study 2, a total of 49 serial biopsy samples were taken from 12 Beagle bitches. In eight bitches, the manipulation resulted in a haemomucometra. Treatment with PGF2 alpha and antibiotics led to a clinical cure in five of these dogs, two of which were mated successfully during the next oestrus. Three animals had to undergo ovariohysterectomy. Owing to the small proportion of biopsy specimens that was suitable for analysis and the high risk of biopsy-related endometritis, transcervical biopsy collection cannot be recommended as a routine technique in bitches.

Correlation of white matter diffusivity and anisotropy with age during childhood and adolescence: a cross-sectional diffusion-tensor MR imaging study

PURPOSE

To evaluate differences in white matter diffusion properties as a function of age in healthy children and adolescents.

MATERIALS AND METHODS

Echo-planar diffusion-tensor magnetic resonance (MR) imaging was performed in 33 healthy subjects aged 5-18 years who were recruited from a functional imaging study of normal language development. Results of neurologic, psychologic, and structural MR imaging examinations were within the normal range for all subjects. The trace of the apparent diffusion coefficient and fractional anisotropy in white matter were correlated as a function of age by using Spearman rank correlation.

RESULTS

Statistically significant negative correlation of the trace of the apparent diffusion coefficient with age was found throughout the white matter. Significant positive correlation of fractional anisotropy with age was found in the internal capsule, corticospinal tract, left arcuate fasciculus, and right inferior longitudinal fasciculus.

CONCLUSION

Diffusion-tensor MR imaging results indicate that white matter maturation assessed at different ages involves increases in both white matter density and organization during childhood and adolescence. The trace of the apparent diffusion coefficient and fractional anisotropy may reflect different physiologic processes in healthy children and adolescents.

Reduced NAA in the thalamus and altered membrane and glial metabolism in schizophrenic patients detected by 1H-MRS and tissue segmentation

Functional and structural abnormalities in the thalamus as well as a generalized phospholipid membrane disorder have been implicated in the pathogenesis of schizophrenic psychosis. To determine whether thalamic neuronal abnormalities and altered membrane-associated metabolites can be detected in schizophrenic patients, we used in vivo proton magnetic resonance spectroscopy (1H-MRS) in 32 acutely-ill, medicated schizophrenic patients and 17 age-matched controls. Thalamic and white matter metabolite concentrations (myo-inositol (mI), choline-containing compounds (Cho), total creatine (Cr) and N-acetylaspartate (NAA)) were estimated and corrected for atrophy (CSF) and gray and white matter contributions (GM, WM) by use of image-based voxel segmentation. Thalamic NAA was significantly reduced in schizophrenic patients, whereas Cho and mI were significantly increased in the parietal white matter. White matter Cr was significantly elevated in patients and correlated positively with the brief psychiatric rating scores (BPRS). Regional metabolite levels were inversely associated with GM and WM content reaching significance for mI and Cr in the thalamus and Cho and NAA in the white matter. Reduced NAA in the left thalamus of schizophrenic patients confirms and extends previous spectroscopic data and agrees well with histologic and imaging findings of reduced neuronal density and volume. Elevated Cho in line with 31P-MRS studies suggests increased myelin degradation thus further supporting a generalized membrane disorder in schizophrenic patients. In addition, we demonstrate the need to correct metabolite concentrations for regional tissue composition in studies employing patients with altered brain morphology.

Fractures of the palmar aspect of the carpal bones in horses: 10 cases (1984-2000)

OBJECTIVE

To determine clinical and radiographic findings, treatment, and outcome of horses with fractures of the palmar aspect of the radial carpal bone, with or without concurrent fractures of the palmar surfaces of the other carpal bones.

DESIGN

Retrospective study.

ANIMALS

10 horses.

PROCEDURE

Medical records were reviewed to obtain information on history, signalment, clinical and radiographic findings, treatment, and outcome. Follow-up information was gathered from owners and referring veterinarians.

RESULTS

7 horses became lame after recovery from general anesthesia for treatment of an unrelated problem. The remaining 3 horses developed a fore-limb lameness after falling (1 horse) or being turned out in a pasture (2 horses). Fractures involved the palmar surface of the radial carpal bone in all 10 horses; in addition, the ulnar carpal bone was affected in 2 horses, the intermediate carpal bone in 2 horses, and the distal aspect of the radius in 4 horses. None of the 4 horses treated nonsurgically returned to work, and 3 were euthanatized because of recalcitrant lameness. In the other 6 horses, fragments were removed surgically. Two were euthanatized because of continued lameness, 1 was euthanatized for other reasons, 2 were sound enough for light work, and 1 returned to athletic work.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that fractures of the palmar aspect of the carpal bones are uncommon in horses. The prognosis appears to be poor for affected horses but may be better for horses that undergo arthroscopic removal of intra-articular fragments.

The HA-2 minor histocompatibility antigen is derived from a diallelic gene encoding a novel human class I myosin protein

Human minor histocompatibility Ags (mHag) present significant barriers to successful bone marrow transplantation. However, the structure of human mHag and the basis for antigenic disparities are still largely unknown. Here we report the identification of the gene encoding the human mHag HA-2 as a previously unknown member of the class I myosin family, which we have designated MYO1G. The gene is located on the short arm of chromosome 7. Expression of this gene is limited to cells of hemopoietic origin, in keeping with the previously defined tissue expression of the HA-2 Ag. RT-PCR amplification of MYO1G from different individuals led to the identification of two genetic variants, designated MYO1G(V) and MYO1G(M). The former encodes the peptide sequence previously shown to be the HA-2 epitope (YIGEVLVSV), whereas the latter shows a single amino acid change in this peptide (YIGEVLVSM). This change has only a modest effect on peptide binding to the class I MHC-restricted element HLA-A*0201, and a minimal impact on recognition by T cells when added exogenously to target cells. Nonetheless, as detected using either T cells or mass spectrometry, this amino acid change results in a failure of the latter peptide to be presented at the surface of cells that express MYO1G(M) endogenously. These studies have thus identified a new mHag-encoding gene, and thereby provide additional information about both the genetic origins of human mHag as well as the underlying basis of an Ag-positive vs Ag-negative state.

Gray matter-changes and correlates of disease severity in schizophrenia: a statistical parametric mapping study

Voxel-based morphometry has recently been used successfully to detect gray matter volume reductions in schizophrenic patients. The aim of the present study was to confirm the findings on gray-matter changes and to complement these by applying the methodology to CSF-differences. Also, we wanted to determine whether a correlation exists between a clinically defined parameter of disease severity and brain morphology in schizophrenic patients. We investigated 48 schizophrenic patients and compared them with 48 strictly age- and sex-matched controls. High-resolution whole-brain MR-images were segmented and analyzed using SPM99. In a further analysis, the covariate effect of the global assessment of functioning-score (GAF) was calculated. Main findings were (i) left-dominant frontal, temporal, and insular GM-reductions and (ii) GM-increases in schizophrenic patients in the right basal ganglia and bilaterally in the superior cerebellum; (iii) CSF-space increases in patients complementary to some GM-reductions; (iv) a correlation between the GAF-score and local GM-volume in the left inferior frontal and inferior parietal lobe of schizophrenic patients. This study confirms and extends some earlier findings on GM-reduction and detected distinct GM-increases in schizophrenic patients. These changes were corroborated by complementary CSF-increases. Most importantly, a correlation could be established between two particular gray matter-regions and the overall disease severity, with more severely ill patients displaying a local GM-deficit. These findings may be of potentially large importance for both the future interpretation and design of neuroimaging studies in schizophrenia and the further elucidation of possible pathophysiological processes occurring in this disease.

Determination of the iron oxidation state in earth materials using XANES pre-edge information

Fe K-edge XANES spectra have been measured in more than 35 Fe(II) and Fe(III)-bearing minerals. The separation between the average pre-edge centroid positions for Fe(II) and Fe(III) is 1.4 +/- 0.1 eV. Examination of calculated pre-edge features of mechanical mixtures of phases containing different proportions of Fe(II) and Fe(III) reveals that different trends of pre-edge position vs. pre-edge intensity can be observed, depending on the coordination environment. Both pre-edge parameters have been used to estimate the ferric/ferrous ratio in 12 natural minerals.

MR diffusion imaging and 1H spectroscopy in a child with medulloblastoma. A case report

We report on a child with a metastasising medulloblastoma which was assessed by MR diffusion imaging and 1H MR spectroscopy (MRS). Reduced mean apparent diffusion coefficients and a high amount of taurine could be demonstrated. This is the first reported case of high taurine in medulloblastoma in vivo and confirms earlier in vitro findings. It is suggested that the changes on diffusion imaging, possibly reflecting the small-cell histology of the tumour and high taurine in MRS, are indicative of medulloblastoma.

[Guidelines of the Spanish Society of Cardiology for clinical practice in exercise testing]

Most exercise testing is performed in adults with known or suspected ischemic heart disease. In the last few years cardiac imaging techniques have been applied in this field, improving the information obtained with the procedure. However, the exceptions to this rule are emerging rapidly not only in healthy people (asymptomatic individuals, athletes, handicapped people) but also in cardiac patients (advanced congestive heart failure, hypertension, rhythm disorders, congenital heart disease, etc.). All the-se issues justify the need for a multidisciplinary consensus document in Spain. This paper reviews and updates the methodological aspects of the stress test, including those related to oxygen consumption measurements. The main aim of this review was to determine the role of exercise testing in the evaluation of ischemic heart disease as well as the applications of imaging stress testing. The usefulness of this test in other non-ischemic cardiac disorders and in selected subsets of healthy people is also reviewed.

Primarily chronic and cerebrovascular course of Lyme neuroborreliosis: case reports and literature review

As part of an ongoing study aiming to define the clinical spectrum of neuroborreliosis in childhood, we have identified four patients with unusual clinical manifestations. Two patients suffered from a primarily chronic form of neuroborreliosis and displayed only non-specific symptoms. An 11 year old boy presented with long standing symptoms of severe weight loss and chronic headache, while the other patient had pre-existing mental and motor retardation and developed seizures and failure to thrive. Two further children who presented with acute hemiparesis as a result of cerebral ischaemic infarction had a cerebrovascular course of neuroborreliosis. One was a 15 year old girl; the other, a 5 year old boy, is to our knowledge the youngest patient described with this course of illness. Following adequate antibiotic treatment, all patients showed substantial improvement of their respective symptoms. Laboratory and magnetic resonance imaging findings as well as clinical course are discussed and the relevant literature is reviewed.

Introduction and evaluation of a modular seminar system in gross anatomy teaching at the Hannover Medical School

We present a new modular seminar system which has been introduced into the gross anatomy teaching at the Hannover Medical School. It consists of seven modules with a clinical emphasis. The new modular seminar system was evaluated by an anonymous questionnaire. The results showed that the seminar system as a whole, and the different modules with one exception were highly appreciated by the students. The evaluation also revealed that the main reason for the success of a module is the manner of the teaching and learning rather than the clinical relevance. Taking into account the results of this evaluation we describe the appropriate style of teaching for use in a seminar. The success of this new approach to small group instruction in Germany should encourage other teachers of anatomy and other undergraduate subjects to consider new methods of teaching.

Genomic identification of the minor histocompatibility antigen HA-1 locus by allele-specific PCR

Graft-versus-host disease (GvHD) can be a major complication of allogeneic bone marrow transplantation even in recipients of HLA genotype-identical transplants. Disparities in minor histocompatibility antigens (mHags) between donor and recipient are a potential risk for the development of GvHD. A mismatch for the mHag HA-1 can cause GvHD in adult recipients of allogeneic bone marrow from HLA-identical donors. The mHag HA-1, first identified by HLA-A*0201-restricted cytotoxic T cells (CTLs), was recently chemically characterized as a nonapeptide. On the cDNA level, the HA-1 locus has two alleles, HA-1H and HA-1R, which differ in two nucleotides, resulting in a single amino acid substitution. Here we report on the genomic structure of the HA-1 locus. Isolation and sequencing of cosmid DNA encoding the HA-1 peptide sequence revealed that the HA-1 alleles are encoded by two exons. Two different primer sets were designed, each consisting of allele-specific primers and a common primer, and both sets containing intronic sequences. We performed genomic DNA typing of three families consisting of 24 HLA-A*0201-positive individuals. The predicted allele-specific products correlated in all cases with the mHag classification by CTLs and by RT-PCR. We demonstrate for the first time the genomic identification of the mHag HA-1 locus. Prospective genomic typing for the HA-1 alleles will improve donor selection and identify HLA-A*0201-positive recipients with a high risk for HA-1-induced GvHD.

Complementation of the genetic defect in Gunn rat hepatocytes in vitro by highly efficient gene transfer with cationic liposomes

In this article, we report complementation of the genetic defect of isolated Gunn rat hepatocytes by a highly efficient method for lipofection. Transfections were performed 24 h after plating by using the cationic liposome DOTAP. On average, transfection efficiencies of 21% lacZ+ cells with Wag/Rij rat cells and 27% lacZ+ cells with Gunn rat cells could be obtained when the parenchymal cells were transfected in a hormone-defined, serum-free medium. LacZ expression vectors with the CMV promoter were more effective than constructs containing the RSV or the TK promoter. A linear relationship between the viability of hepatocytes after isolation and the percentage of lacZ+ cells was observed with both rat strains, with a maximum of 40% lacZ+ cells at a viability of 94%. The transfection efficiencies were significantly lower in the absence of growth factors, in dexamethasone-containing medium, or when serum was present during plating. Our data are consistent with the assumption that a mitotic event is required for efficient lipofection. Bilirubin conjugation activity could be detected in microsomes from Gunn rat hepatocytes after transfection with two different B-UDPGT expression constructs. Highest conjugation activity was achieved with a vector containing a terminal intron. With this construct on average 4% of the bilirubin conjugation activity of normal human liver microsomes could be achieved in total microsomes of transfected Gunn rat hepatocytes. The implications of our data for gene therapy of hepatic disease with nonviral vectors, in particular bilirubin conjugation deficiency (Crigler-Najjar disease) are discussed.

Characterization of a large transferrin-binding protein from Actinobacillus pleuropneumoniae serotype 7

The binding of transferrin at the surface of Actinobacillus pleuropneumoniae (A. pp.) is mediated by two proteins of approximately 60 and 100 kDa. The 60 kDa protein has been shown to be highly divergent among different serotypes and to induce a serotype-specific protective immune response. In this study we have characterized the 100 kDa transferrin-binding protein of A. pp. serotype 7 and designated it as TfbB. The tfbB gene was found to be located immediately downstream of the tfbA gene. It was cloned and sequenced, and antibodies raised against the isolated recombinant protein detected, with a constant intensity, a 100 kDa protein in A. pp. serotypes 2, 4, 6, 7, 8, 9, 10 and 11, and a polypeptide of approximately 103 kDa in serotypes 1, 3, 5A and 12. In addition, comparative analysis of the deduced amino acid sequence showed more than 40% identity with the large transferrin-binding proteins of Neisseria meningitidis and Haemophilus influenzae. The TfbB protein was expressed in E. coli outer membranes in a conformation eliciting porcine transferrin-specific binding activity. Sera of pigs immunized with these TfbB-containing E. coli membranes recognized functional membrane-associated TfbB protein whereas no such reaction was observed upon immunization with isolated recombinant TfbB protein. A preliminary animal experiment showed that TfbB-containing outer membrane preparations from recombinant E. coli can reduce significantly the mortality of an A.pp. infection with the homologous strain.

Efficacy of a peptide-based gene delivery system depends on mitotic activity

We have developed and tested a transfection compound based on synthetic peptides. It consists of a 12 amino acid DNA binding peptide (P2) with an alkyl group added to the aminoterminus (P2lip) and a peptide derived from the hemagglutinin protein (HA). The components aggregate spontaneously to particles that proved to be an efficient, easy to use and chemically stable transfection compound. With this system we found a marked correlation between transfection efficiency and mitotic activity. Cells that are allowed to perform a mitosis after exposure to either DNA-P2lip/HA or DNA-cationic liposome complexes are transfected much more efficiently than cells arrested in the cell cycle. In search of an explanation for this phenomenon we studied transport of plasmid DNA across the nuclear membrane. Plasmid DNA injected into the cytoplasm of quiescent human fibroblasts is not expressed, in contrast to DNA injected into the nucleus. FISH analysis showed that the plasmid DNA is not transported into the nucleus efficiently. Similarly, DNA-P2lip/HA complexes are readily taken up by both proliferating and nonproliferating cells, but do not readily penetrate the nuclear membrane. We conclude that delivery of plasmid DNA to the cytoplasm is not sufficient for transfection of eukaryotic cells. The nuclear membrane is apparently an important barrier. This explains why a mitotic event is required for efficient transfection with the currently available transfection systems. The implications for the further development of transfection compounds for use in vivo, where nonproliferating cells are often the target, are discussed.

Positional mapping of loci in the DiGeorge critical region at chromosome 22q11 using a new marker (D22S183)

The majority of patients with DiGeorge syndrome (DGS) and velo-cardio-facial syndrome (VCFS) and a minority of patients with non-syndromic conotruncal heart defects are hemizygous for a region of chromosome 22q11. The chromosomal region that is commonly deleted is larger than 2 Mb. It has not been possible to narrow the smallest region of overlap (SRO) of the deletions to less than ca 500 kb, which suggests that DGS/VCFS might be a contiguous gene syndrome. The saturation cloning of the SRO is being carried out, and one gene (TUPLE1) has been identified. By using a cosmid probe (M51) and fluorescence in situ hybridization, we show here that the anonymous DNA marker locus D22S183 is within the SRO, between TUPLE1 and D22S75 (probe N25). A second locus with weak homology to D22S183, recognized by cosmid M56, lies immediately outside the common SRO of the DGS and VCFS deletions, but inside the SRO of the DGS deletions. D22S183 sequences are strongly conserved in primates and weaker hybridizing signals are found in DNA of other mammalian species; no transcripts are however detected in polyA+ RNA from various adult human organs. Probe M51 allows fast reliable screening for 22q11 deletions using fluorescence in situ hybridization. A deletion was found in 11 out of 12 DGS patients and in 3 out of 7 VCFS patients. Two patients inherited the deletion from a parent with mild (atypical) symptoms.