Mutation screening and LD mapping in the VCFS deleted region of chromosome 22q11 in schizophrenia using a novel DNA pooling approach

We examined whether variation within six genes from the VCFS critical region at 22q11 (DGSC, Stk22A1, DGSI, Gscl, Slc25A1 and Znf74) confers susceptibility to schizophrenia. We screened the exons and flanking intronic sequence of each gene for mutations in 14 individuals with DSM-IV schizophrenia using DHPLC. All polymorphisms identified were characterised and genotyped in a sample of 184 schizophrenics and matched controls, using novel DNA pooling methods. Of the polymorphisms identified, 17 were located within exons, six were within coding sequence, and two were non-synonymous. Pooled genotyping revealed no differences in the allele frequencies for any polymorphism between cases and controls that met our pre-defined criterion (P < or = 0.1). In a complementary approach we also attempted to define the location of a schizophrenia susceptibility locus more precisely by performing association mapping using seven microsatellites spanning the VCFS region with an average inter-marker distance of 450 kb. Conventional chi(2) analysis of genotypes in 368 cases and 368 controls revealed that none of the markers was significantly associated (P < 0.05) with schizophrenia. However, evidence for significant association (P = 0.003) was obtained for D22S944 when alleles were combined. TDT analysis of D22S944 genotyped in a further 278 cases of schizophrenia and their parents failed to find any overall allele-wise significant transmission disequilibrium (chi(2) = 18.3, P = 0.17). However, individual analysis of the alleles revealed that allele 12 was excessively non-transmitted and that this almost reached significance when corrected for multiple alleles (chi(2) = 7.35, P = 0.006, P = 0.078 corrected for 13 alleles).

A haplotype implicated in schizophrenia susceptibility is associated with reduced COMT expression in human brain

The gene encoding catechol-O-methyltransferase (COMT) is a strong candidate for schizophrenia susceptibility, owing to the role of COMT in dopamine metabolism, and the location of the gene within the deleted region in velocardiofacial syndrome, a disorder associated with high rates of schizophrenia. Recently, a highly significant association was reported between schizophrenia and a COMT haplotype in a large case-control sample (Shifman et al. 2002). In addition to a functional valine-->methionine (Val/Met) polymorphism, this haplotype included two noncoding single-nucleotide polymorphisms (SNPs) at either end of the COMT gene. Given the role of COMT in dopamine catabolism and that deletion of 22q11 (containing COMT) is associated with schizophrenia, we postulated that the susceptibility COMT haplotype is associated with low COMT expression. To test this hypothesis, we have applied quantitative measures of allele-specific expression using mRNA from human brain. We demonstrate that COMT is subject to allelic differences in expression in human brain and that the COMT haplotype implicated in schizophrenia (Shifman et al. 2002) is associated with lower expression of COMT mRNA. We also show that the 3' flanking region SNP that gave greatest evidence for association with schizophrenia in that study is transcribed in human brain and exhibits significant differences in allelic expression, with lower relative expression of the associated allele. Our results indicate that COMT variants other than the Val/Met change are of functional importance in human brain and that the haplotype implicated in schizophrenia susceptibility is likely to exert its effect, directly or indirectly, by down-regulating COMT expression.

Mutation screening of the Homer gene family and association analysis in schizophrenia

Homer proteins are a group of proteins that regulate group 1 metabotropic glutamate receptor function. As altered glutamate function has been implicated in many neuro psychiatric disorders, particularly schizophrenia, we have screened all three known Homer genes for sequence variation for use under the candidate gene association paradigm. We found seven SNPs, including three in exons. Of these, none was non-synonymous. Allele frequencies of all the detected SNPs were estimated in DNA pools of 368 schizophrenics and 368 controls. Only one (Homer 1 IVS4 + 18A > G) was associated with schizophrenia in this sample, a finding confirmed by individual genotyping (P = 0.01). However, in our extended sample of 680 cases and 671 controls, the evidence for association diminished (P = 0.05). Our results suggest it is unlikely that sequence variants in the Homer genes contribute to the aetiology of schizophrenia, but the variants we identified are plausible candidates for other neuropsychiatric phenotypes.

Genome scan meta-analysis of schizophrenia and bipolar disorder, part II: Schizophrenia

Schizophrenia is a common disorder with high heritability and a 10-fold increase in risk to siblings of probands. Replication has been inconsistent for reports of significant genetic linkage. To assess evidence for linkage across studies, rank-based genome scan meta-analysis (GSMA) was applied to data from 20 schizophrenia genome scans. Each marker for each scan was assigned to 1 of 120 30-cM bins, with the bins ranked by linkage scores (1 = most significant) and the ranks averaged across studies (R(avg)) and then weighted for sample size (N(sqrt)[affected casess]). A permutation test was used to compute the probability of observing, by chance, each bin's average rank (P(AvgRnk)) or of observing it for a bin with the same place (first, second, etc.) in the order of average ranks in each permutation (P(ord)). The GSMA produced significant genomewide evidence for linkage on chromosome 2q (PAvgRnk<.000417). Two aggregate criteria for linkage were also met (clusters of nominally significant P values that did not occur in 1,000 replicates of the entire data set with no linkage present): 12 consecutive bins with both P(AvgRnk) and P(ord)<.05, including regions of chromosomes 5q, 3p, 11q, 6p, 1q, 22q, 8p, 20q, and 14p, and 19 consecutive bins with P(ord)<.05, additionally including regions of chromosomes 16q, 18q, 10p, 15q, 6q, and 17q. There is greater consistency of linkage results across studies than has been previously recognized. The results suggest that some or all of these regions contain loci that increase susceptibility to schizophrenia in diverse populations.

Support for genetic variation in neuregulin 1 and susceptibility to schizophrenia

Recently, it has been reported that genetic variants around the gene neuregulin 1 are associated with schizophrenia in an Icelandic sample. Of particular interest was the presence of a single-risk haplotype that was significantly over-represented in schizophrenic individuals compared to controls (15.4 : 7.5%, P=6.7 x 10(-6)). We have attempted to replicate this result in our large collection of 573 schizophrenia cases and 618 controls. We found that the risk haplotype was more common in cases than controls (9.5 : 7.5%; P=0.04), and especially in our subset of 141 cases with a family history of schizophrenia (11.6%; P=0.019). Our results therefore replicate the Icelandic findings in an out-bred Northern European population, although they suggest that the risk conferred by the haplotype is small.

Determination of the genomic structure and mutation screening in schizophrenic individuals for five subunits of the N-methyl-D-aspartate glutamate receptor

The glutamatergic system is the major excitatory neurotransmitter system in the CNS. Glutamate receptors, and in particular N-methyl-D-aspartate (NMDA) receptors, have been proposed as mediators of many common neuropsychiatric phenotypes including cognition, psychosis, and degeneration. We have reconstructed the genomic structure of all five genes encoding NMDA receptors in silico. We screened each for sequence variation and estimated the allele frequencies of all detected SNPs in pooled samples of 184 UK Caucasian schizophrenics and 184 UK Caucasian blood donor controls. Only a single non-synonymous polymorphism was found indicating extreme selection pressure. The rarity of non-synonymous changes suggests that such variants are unlikely to make a common contribution to common phenotypes. We found a further 26 polymorphisms within exonic or adjacent intronic sequences. The minor alleles of most of these have a relatively high frequency (63% above 0.2). These SNPs will therefore be suitable for studying neuropsychiatric phenotypes that are putatively related to NMDA dysfunction. Pooled analysis provided no support for association between any of the GRIN genes and schizophrenia.

Crossiella equi sp. nov., isolated from equine placentas

Over the course of the past decade, actinomycetes have been isolated from the placentas of horses diagnosed with nocardioform placentitis. The incidence of this infection has generally been low, with typically no more than 30 animals affected in most years, but the incidence increased through 1999, with placentas from 144 mares found to be infected. Approximately half of the cases result in loss of the foal. A typical actinomycete with branching mycelium was isolated from placental lesions, and a comparison of the sequence of the 16S rDNA gene against the public databases indicated a relationship to members of the suborder Pseudonocardineae. Phylogenetic analysis of representative isolates revealed a close relationship to Crossiella cryophila, and subsequent polyphasic comparisons determined that these isolates represent a novel species of Crossiella, for which the name Crossiella equi sp. nov. is proposed, with strain LDDC 22291-98(T) (= NRRL B-24104(T) = DSM 44580(T)) as the type strain.

Schizophrenia and functional polymorphisms in the MAOA and COMT genes: no evidence for association or epistasis

Several lines of evidence suggest that psychosis is associated with altered dopaminergic neurotransmission. Dopamine is catabolized by monoamine oxidase (MAO) and catechol-O-methyl transferase (COMT). We hypothesized that the genes encoding MAOA and COMT might contain genetic variation conferring increased risk to schizophrenia. In order to test this hypothesis, we genotyped the 941T > G and the promoter VNTR polymorphisms in the MAOA gene and the V158M COMT polymorphism in 346 DSMIV schizophrenics and 334 controls. We also genotyped the-287A > G COMT promoter polymorphism in 177 schizophrenics and 173 controls. No significant differences were found in allele or genotype frequencies between affecteds and controls for any of the polymorphisms. As both genes are involved in degrading catecholamines, we also sought evidence for additive and epistatic effects but none was observed. Our data, therefore, do not support the hypothesis that genetic variation in MAOA and COMT is involved individually or in combination in the etiology of schizophrenia.

Universal, robust, highly quantitative SNP allele frequency measurement in DNA pools

Detecting alleles that confer small increments in susceptibility to disease will require large-scale allelic association studies of single-nucleotide polymorphisms (SNPs) in candidate, or positional candidate, genes. However, current genotyping technologies are one to two orders of magnitude too expensive to permit the analysis of thousands of SNPs in large samples. We have developed and thoroughly validated a highly accurate protocol for SNP allele frequency estimation in DNA pools based upon the SNaPshot (Applied Biosystems) chemistry adaptation of primer extension. Using this assay, we were able to estimate the difference in allele frequencies between pooled cases and controls (Delta) with a mean error of 0.01. Moreover, when we genotyped seven different SNPs in a single multiplex reaction, the results were similar, with a mean error for Delta of 0.008. The assay performed well for alleles of low frequency alleles (f approximately 0.05) and was accurate even with relatively poor quality DNA template extracted from mouthwashes. Our assay conditions are generalisable, universal, robust and, therefore, for the first time, permit high-throughput association analysis at a realistic cost.

No major schizophrenia locus detected on chromosome 1q in a large multicenter sample

Reports of substantial evidence for genetic linkage of schizophrenia to chromosome 1q were evaluated by genotyping 16 DNA markers across 107 centimorgans of this chromosome in a multicenter sample of 779 informative schizophrenia pedigrees. No significant evidence was observed for such linkage, nor for heterogeneity in allele sharing among the eight individual samples. Separate analyses of European-origin families, recessive models of inheritance, and families with larger numbers of affected cases also failed to produce significant evidence for linkage. If schizophrenia susceptibility genes are present on chromosome 1q, their population-wide genetic effects are likely to be small.

Cultures of equine respiratory epithelial cells and organ explants as tools for the study of equine influenza virus infection

Equine nasal turbinate epithelial cells and tracheal rafts were maintained with sustained viability in culture. Both types of culture supported productive replication of equine influenza virus (equine-2, subtype H3N8) and cell death occurred through apoptosis following viral infection. Thus, primary respiratory epithelial cell and organ cultures of equine origin may be valuable as alternatives to the intact animal for studying the virus-host interaction of equine respiratory viruses including influenza.

Genome scans and microarrays: converging on genes for schizophrenia?

Systematic genome-wide scans to date have shown that genes of major effect are not common causes of schizophrenia, but independent linkage studies looking for schizophrenia susceptibility genes are converging on a number of key chromosomal locations. Microarray expression analysis may identify new candidate genes and pathways, and a number of intriguing preliminary findings have already been reported.

The first reported case of equine nocardioform placentitis in South Africa

Since the late 1980s a distinct form of focally-extensive mucoid to mucopurulent uterine body chronic placentitis,caused by nocardioform organisms, hasbeen recognised in horses in the USA state of Kentucky and possibly in other areas. This disease has led to increasing numbers of foal losses from late abortions, still-births, prematurity, or early neonatal deaths. The foals are usually not infected, but may be small or emaciated. Modes of infection and transmission are as yet unknown. Nocardia spp. and related nocardioform bacteria as causes of equine infertility, endometritis and foal death are briefly reviewed. A case of near full-term abortion involving a Friesian mare in the Pretoria district of Gauteng Province in South Africa during February 2000, with the same placental lesion as described in the Kentucky cases, is presented. Nocardioform organisms were visualised on impression smears and histological sections of affected foetal membranes, and were also cultured. The organism has been identified at the Livestock Disease Diagnostic Center of the University of Kentucky as an Amycolatopsis sp. of the less-commonly diagnosed group of nocardioforms causing placentitis in the USA. The organism was cultured from the uterus of the mare 18 days post-foaling, but after a 2-week course of oral trimethoprim and sulphamethoxazole, based on antibiogram sensitivity testing, a uterine flush yielded no growth. A semen sample from the sire of the aborted foal did not yield any Gram-positive filamentous branching bacteria. The mare subsequently conceived to a single insemination.

A genomewide linkage study of age at onset in schizophrenia

There is strong evidence for a genetic contribution to age at onset of schizophrenia, which probably involves both susceptibility loci for schizophrenia and modifying loci acting independent of disease risk. We sought evidence of linkage to loci that influence age at onset of schizophrenia in a sample of 94 affected sibling pairs with DSM-IV schizophrenia or schizoaffective disorder, and age at first psychiatric contact of 45 years or less. Individuals were genotyped for 229 microsatellite markers spaced at approximately 20 cM intervals throughout the genome. Loci contributing to age at onset were sought by a quantitative maximum-likelihood multipoint linkage analysis using MAPMAKER/SIBS. A nonparametric multipoint analysis was also performed. The genomewide significance of linkage results was assessed by simulation studies. There were six maximum-likelihood LOD score peaks of 1.5 or greater, the highest being on chromosome 17q (LOD = 2.54; genomewide P = 0.27). This fulfils Lander and Kruglyak's [1995: Nat Genet 11:241-247] criteria for suggestive linkage in that it would be expected to occur once or less (0.3 times) per genome scan. However, this finding should be treated with caution because the LOD score appeared to be almost solely accounted for by the pattern of ibd sharing at one marker (D17S787), with virtually no evidence of linkage over flanking markers. None of the linkage results achieved genomewide statistical significance, but the LOD score peak on chromosome 13q (LOD = 1.68) coincided with the region showing maximum evidence for linkage in the study by Blouin et al. [1998: Nat Genet 20:70-73] of categorical schizophrenia.

Association analysis of NOTCH4 loci in schizophrenia using family and population-based controls

A genetic association between NOTCH4 and schizophrenia has previously been proposed. Unsing all markers previously shown to be associated, we found no evidence for such in three independent family-based samples (n=519 parent-offspring trios), and a case-control sample derived from the same ethnic background as the original observation. These data strongly suggest that NOTCH4 is not a significant susceptibility allele for schizophrenia.

Emergent causes of placentitis and abortion

The clinical signs, laboratory findings, diagnosis, epidemiology, treatment, and prevention and control of two emerging causes of placentitis and abortion in horses are described in this article. Leptospirosis has been reported as a significant cause of fetal loss in horses in Kentucky, Northern Ireland, and England. Most abortions result from infection by serovars kennewicki or bratislava. Nocardioform placentitis has become the most common cause of placentitis in central Kentucky horses. Nocardioform placentitis is associated with infection by unnamed, gram-positive, filamentous, branching bacteria, and is characterized by distinctive changes in the placental membranes.

Multicenter linkage study of schizophrenia candidate regions on chromosomes 5q, 6q, 10p, and 13q: schizophrenia linkage collaborative group III

Schizophrenia candidate regions 33-51 cM in length on chromosomes 5q, 6q, 10p, and 13q were investigated for genetic linkage with mapped markers with an average spacing of 5.64 cM. We studied 734 informative multiplex pedigrees (824 independent affected sibling pairs [ASPs], or 1,003 ASPs when all possible pairs are counted), which were collected in eight centers. Cases with diagnoses of schizophrenia or schizoaffective disorder (DSM-IIIR criteria) were considered affected (n=1,937). Data were analyzed with multipoint methods, including nonparametric linkage (NPL), ASP analysis using the possible-triangle method, and logistic-regression analysis of identity-by-descent (IBD) sharing in ASPs with sample as a covariate, in a test for intersample heterogeneity and for linkage with allowance for intersample heterogeneity. The data most supportive for linkage to schizophrenia were from chromosome 6q; logistic-regression analysis of linkage allowing for intersample heterogeneity produced an empirical P value <.0002 with, or P=.0004 without, inclusion of the sample that produced the first positive report in this region; the maximum NPL score in this region was 2.47 (P=.0046), the maximum LOD score (MLS) from ASP analysis was 3.10 (empirical P=.0036), and there was significant evidence for intersample heterogeneity (empirical P=.0038). More-modest support for linkage was observed for chromosome 10p, with logistic-regression analysis of linkage producing an empirical P=. 045 and with significant evidence for intersample heterogeneity (empirical P=.0096).

No evidence for association between a non-synonymous polymorphism in the gene encoding human metabotropic glutamate receptor 7 and schizophrenia

The cDNA sequence of the gene encoding human metabotropic glutamate receptor type 7 (mGluR7) contains the single nucleotide polymorphism 1536A > T [GenBank sequence X94552 (Makoff et al., 1996)]. This sequence variation is predicted to result in an amino acid change (F433Y) in the gene product and thus has the potential to affect receptor function. Since disturbances in glutamate function have been implicated in the pathophysiology of schizophrenia, we have used a novel and robust polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay to genotype this polymorphism in a case-control sample comprising 181 schizophrenic patients and 182 group-matched unaffected individuals. No evidence was found for association between this polymorphism and schizophrenia. We have also localised mGluR7 to chromosome 3p25-22 using radiation hybrid (RH) mapping.

Thoughts on the source of tissue on subsequent cell culture success

This paper describes attempts to initiate equine adipocyte cultures from necropsy cases with varying intervals from time of death to isolation and culture. Equine adipocytes were isolated from 21 necropsy cases, regardless of the interval from time after death to establishment in primary ceiling cultures. However, while all cultures produced adipocytes, only 2 attempts to produce long-term equine adipocyte cultures from the subcutaneous rump fat depots were successful and not contaminated. Findings from these experiments indicate that it is possible to collect and culture equine adipocytes from necropsy cases with varying intervals of time of death to culturing provided that the issue of contamination is addressed. Viable cells were produced from tissue with an interval of 38.5 hours as well as 45 minutes. This result encourages the continuation of research using equine necropsy cases as a source of adipose tissue.

A two-stage genome scan for schizophrenia susceptibility genes in 196 affected sibling pairs

We undertook a systematic search for linkage in 196 affected sibling pairs (ASPs) with DSMIV schizophrenia. In stage 1 we typed 97 ASPs with 229 microsatellite markers at an average inter-marker distance of 17.26 cM. Multipoint affected sib pair analysis identified seven regions with a maximum lod score (MLS) at or above the level associated with a nominal pointwise significance of 5%, on chromosomes 2q, 4p, 10q, 15q, 18p, 20q and Xcen. In stage 2 we genotyped a further 54 markers in 196 ASPs together with parents and unaffected siblings. This allowed the regions identified in stage 1 to be typed at an average spacing of 5.15 cM, while the region of interest on chromosome 2 was typed to 9.55 cM. Analysis was performed on the whole data set. Simulation studies suggested that we would expect one multipoint MLS of 1.5 per genome scan in the absence of linkage. An MLS of 3 would be expected only once in every 20 genome scans and thus corresponds to a genome-wide significance of 0.05. We obtained three multipoint MLSs >1.5 and, on this basis, the results on chromosomes 4p, 18q and Xcen can be considered suggestive. However, none approached a genome-wide significance of 0. 05. The power of this study was >0.95 to detect a susceptibility locus of lambda(s)= 3 with a genome-wide significance of 0.05, but only 0.70 to detect a locus of lambda(s)= 2. Our results suggest that common genes of major effect (lambda(s)> 3) are unlikely to exist for schizophrenia.

Autosome search for schizophrenia susceptibility genes in multiply affected families

We have analysed 298 polymorphic markers in 13 families multiply affected with schizophrenia and related disorders using a combination of radiolabelled and fluorescent-based methodologies. The markers were distributed throughout the autosomes at an average spacing of 12.8 cM. The data were analysed with two-point linkage analysis (MLINK) and heterogeneity testing (HOMOG). Several genetic models were used ranging from near dominant to fully recessive. Multi-point analysis was performed for 27 regions demonstrating either contiguously positive lod scores in two or more consecutive markers, and in regions with two-point lod score(s) of 1.0 or above in a single marker. A proportion of the multi-point regions have been implicated in previous studies, thereby decreasing risk of false-positive results. However neither our two-point, nor multi-point scores reached the threshold value for significance of 3. 6. Nevertheless three regions were suggestive of linkage.

CAG repeat length in the hKCa3 gene and symptom dimensions in schizophrenia

BACKGROUND

Long CAG repeats in the hKCa3 potassium channel gene have been associated with schizophrenia. We sought evidence for associations between this polymorphism and aspects of the schizophrenia phenotype.

METHODS

Associations were investigated between CAG repeat length and gender, age of illness onset, and psychotic symptom dimensions in 203 unrelated individuals with DSM-IIIR schizophrenia.

RESULTS

No association was found between CAG repeat length and gender or age of onset. Long CAG repeats were associated with higher negative symptom dimension scores.

CONCLUSIONS

This study provides preliminary evidence that genetic liability to negative symptoms in schizophrenia may be partly mediated through the hKCa3 gene.

DNA pooling identifies QTLs on chromosome 4 for general cognitive ability in children

General cognitive ability (g), which is related to many aspects of brain functioning, is one of the most heritable traits in neuroscience. Similarly to other heritable quantitatively distributed traits, genetic influence on g is likely to be due to the combined action of many genes of small effect [quantitative trait loci (QTLs)], perhaps several on each chromosome. We used DNA pooling for the first time to search a chromosome systematically with a dense map of DNA markers for allelic associations with g. We screened 147 markers on chromosome 4 such that 85% of the chromosome were estimated to be within 1 cM of a marker. Comparing pooled DNA from 51 children of high g and from 51 controls of average g, 11 significant QTL associations emerged. The association with three of these 11 markers ( D4S2943, MSX1 and D4S1607 ) replicated using DNA pooling in independent samples of 50 children of extremely high g and 50 controls. Furthermore, all three associations were confirmed when each individual was genotyped separately ( D4S2943, P = 0. 00045; MSX1, P = 0.011; D4S1607, P = 0.019). Identifying specific genes responsible for such QTL associations will open new windows in cognitive neuroscience through which to observe pathways between genes and learning and memory.

The diagnostic value of symptoms and signs in childhood abdominal pain

The assessment and diagnosis of abdominal pain in childhood continues to be a clinical challenge. We audited the presenting symptoms and signs in a consecutive series of 447 children presenting to a paediatric surgical unit in an attempt to quantify the value of particular symptoms and signs in differentiating acute appendicitis (AA) from non-specific abdominal pain (NSAP). The onset of pain in the centre of the abdomen and radiation of pain was not sufficient to differentiate between NSAP and AA. Progression of pain, nausea, vomiting, anorexia and diarrhoea were significantly more common in children with AA (P < 0.01). Similarly, facial flushing, tachycardia (pulse > 100 beats/min), guarding and rebound tenderness were significantly more common in children with AA (P < 0.001). Knowledge of this quantitative data could help clinicians adjust the weighting given to the presence of a particular symptom or sign in children with acute abdominal pain.

Further support for an association between a polymorphic CAG repeat in the hKCa3 gene and schizophrenia

A recent study has suggested that a polymorphism in the hKCa3 potassium channel may be associated with raised susceptibility to schizophrenia. Despite its modest statistical significance, the study is intriguing for two reasons. First, hKCa3 contains a polymorphic CAG repeat in its coding sequence, with large repeats more common in schizophrenics compared with controls. This is interesting in view of several repeat expansion detection (RED) studies that have reported an excess of large CAG repeats in psychotic probands. Second, the hKCa3 gene is a functional candidate gene because studies of antipsychotic and psychotogenic compounds suggest that glutamatergic systems modulated by SKCa channels may be important in schizophrenia pathogenesis. In the light of the above, we have tested the hypothesis of an association between schizophrenia and the hKCa3 CAG repeat polymorphism using a case control study design. Under the same model of analysis as the earlier study, schizophrenic probands had a higher frequency of alleles with greater than 19 repeats than controls (chi 2 = 2.820, P = 0.047, 1-tail). Our data therefore provide modest support for the hypothesis that polymorphism in the hKCa3 gene may contribute to susceptibility to schizophrenia.

Magnetic resonance imaging in a spinal abscess model. Preliminary report

RATIONAL AND OBJECTIVES

Magnetic resonance (MR) scan technique and lesion detectability were evaluated using a newly developed spinal abscess model in the New Zealand White rabbit.

METHODS

To create the lesion, an epidural needle was inserted under fluoroscopic guidance in the lumbar region and advanced to penetrate the ligamentum flavum. Next, polyethylene tubing was fed through the needle into the epidural space. A mixed suspension of Staphylococcus aureus (Cowan I) and blue polystyrene microspheres then was injected. Lesions were evaluated by MR imaging in four animals at multiple time points (3, 6, and 9 days). Imaging was performed at 1.5 tesla using a surface coil. Precontrast T2-and T1-weighted scans were first obtained. The T1-weighted scans were acquired both with and without fat saturation, and were repeated after intravenous contrast administration. The contrast agent used was gadoteridol (gadolinium HP-DO3A or ProHance) at a dose of 0.3 mmol/kg.

RESULTS

On prospective film review, postcontrast scans proved superior for lesion detection. A spinal abscess could be identified postcontrast in all cases, irrespective of the use of fat saturation. The next best imaging technique for lesion detection was the T2-weighted scan, with 5 of 8 lesions noted thereon. Visualization of lesion margins proved to be a primary factor in prospective lesion identification. Region of interest image analysis demonstrated the postcontrast scans to be superior to all precontrast scan techniques for conspicuity of the interface between the abscess and the compressed spinal cord, with these results statistically significant. The lesions were characterized histologically by infiltrates of heterophils into the meninges and outer spinal cord with accompanying mild hemorrhage, fibrin exudation, and bacterial colonies. The lesions in three animals were confirmed to be in the epidural space, with the lesion in one animal in the subdural space.

CONCLUSIONS

The current animal model was developed to study spine infection and, specifically, imaging characteristics and lesion detectability on MR. With the increased use of epidural catheters for pain management and the large number of acquired immunodeficiency syndrome cases, epidural infection is becoming an increasingly important clinical problem. Imaging technique, in particular the use of intravenous contrast, is critical for lesion detection and evaluation.

Is the incidence of acute appendicitis really falling?

To determine if there has been a genuine fall in the incidence of acute appendicitis, an epidemiological study using HAA and Korner datasets for the years 1975-1994 was carried out to identify those children and young adults undergoing appendicectomy for acute appendicitis. The overall incidence of acute appendicitis fell from 1.84/1000 to 1.17/1000. This fall was statistically significant (R2 = 0.74, P < 0.01). The decrease was significant in both males (overall reduction, 34%) and females (overall reduction, 40%). No significant reduction was observed in either males or females between 15 and 19 years of age. The overall reduction remains essentially unexplained, but may have implications for health planning and provision of services.

Dynamic contrast-enhanced magnetic resonance imaging in a model of splenic metastasis

RATIONALE AND OBJECTIVES

The use of rapid dynamic magnetic resonance (MR) imaging after bolus intravenous contrast injection, to improve detection and delineation of parenchymal disease, was evaluated in an experimental model of splenic metastasis.

METHODS

An experimental model for splenic metastasis was first developed in the New Zealand White rabbit. Magnetic resonance studies were then obtained at 1.5 tesla in six animals. A 25 ga needle was used to penetrate the spleen and inject 0.1 mL of minced, screened VX2 adenocarcinoma (obtained from a carrier rabbit). The injections were performed by two techniques, percutaneously using ultrasound guidance (n = 3) and at the time of abdominal laparotomy (n = 3). The animals were imaged at 1.5 tesla on day 10 after implantation. Breath-hold T2-weighted and T1-weighted scans were acquired prior to contrast injection. A dose of 0.3 mmol/kg gadoteridol (ProHance) was then administered intravenously using an MR-compatible power injector, with both dynamic and delayed postcontrast scans obtained. The lesion was confirmed in each animal by gross pathologic and microscopic exam.

RESULTS

On region of interest analysis of T2-weighted scans, the lesions could not be differentiated by signal intensity (with any statistical significance) from normal surrounding splenic parenchyma. Lesion conspicuity, assessed by signal difference/noise ratio on dynamic turbo-FLASH scans, increased from 6+/-5 precontrast to a peak of 16+/-5 at 31 seconds postcontrast, with P < 0.003 (n = 6). Lesion conspicuity steadily diminished from this time to 5 minutes postinjection, although it was still improved at 5 minutes over precontrast scans.

CONCLUSIONS

On early dynamic contrast enhanced breath-hold MR, marked improvement in the differentiation of splenic metastases from surrounding normal parenchyma is achieved. The capability of dynamic MR in this regard is analogous to that demonstrated for helical computed tomography.

Magnetic resonance imaging of experimental pyelonephritis in rabbits

RATIONALE AND OBJECTIVES

An experimental model of acute focal pyelonephritis was developed in the New Zealand White rabbit, with initial imaging evaluation performed using high-field contrast-enhanced magnetic resonance (MR) in six animals.

METHODS

The left kidney was visualized fluoroscopically after intravenous injection of iodinated contrast. A 0.1 mL mixture of agarose/Streptococcus faecalis was then injected percutaneously into the kidney at the corticomedullary junction with a 25-gauge needle. The animals were imaged at 1.5 tesla on day 5 after injection of bacteria. Breathhold T2-weighted and T1-weighted scans were acquired prior to contrast injection. Using an MR-compatible power injector, 0.3 mmol/kg gadoteridol was then administered, with both dynamic and delayed postcontrast scans obtained. The lesion was confirmed in each animal by gross and microscopic exam.

RESULTS

The area of acute focal pyelonephritis was somewhat difficult to identify on precontrast scans. The lesion was mildly hyperintense on T2-weighted scans and slightly hypointense to isointense on T1-weighted scans relative to normal surrounding renal parenchyma. On early dynamic turbo-fast low-angle shot scans, the lesion could be identified due to differential tissue enhancement. Direct visualization of the lesion, with increased conspicuity relative to precontrast scans, was possible because of delayed positive enhancement at 60 seconds postcontrast. Lesion conspicuity, assessed by signal difference/noise ratio, increased from 0 +/- 5 precontrast to a peak of 12 +/- 6 at 60 seconds postcontrast (P = 0.003; n = 6).

CONCLUSIONS

On dynamic contrast-enhanced MR, acute focal pyelonephritis can demonstrate transient positive contrast enhancement (using a contrast dose of 0.3 mmol/kg) relative to surrounding normal renal parenchyma. This appearance is due to hyperconcentration of the contrast agent in normal parenchyma and T2 effects. The pattern is opposite that seen in spiral computed tomography.

Contrast-enhanced magnetic resonance imaging in a spinal epidural tumor model

RATIONALE AND OBJECTIVES

A spinal epidural tumor model was developed, using the VX-2 adenocarcinoma in rabbits, to assess the strengths and weaknesses of magnetic resonance (MR) as a cross-sectional imaging modality for the evaluation of epidural neoplastic disease. High-resolution MR images were acquired both before and after intravenous gadolinium chelate injection, assessing lesion detectability and efficacy of imaging technique.

METHODS

An adenocarcinoma tumor (VX-2) was produced in the epidural space of six New Zealand White rabbits and subsequently studied on a 1.5 tesla whole body MR scanner. VX-2 tumor tissue was removed from the thigh of a carrier rabbit, minced, and screened. Under fluoroscopic guidance, 0.2 mL of the tumor preparation was then injected into the epidural space of the experimental rabbits. The injection was performed at the L5-6 level using an epidural needle and polyethylene tubing sleeved within the needle. The rabbits were imaged using a circular small parts surface coil 5 to 15 days after the epidural injection. In all six animals, one complete MR exam was obtained within the time frame of days 9 to 11. T1- and T2-weighted axial scans were obtained before contrast injection, with the T1 scans acquired both with and without fat saturation. Postcontrast T1 scans also were obtained, using fat saturation, after the injection of 0.1 and 0.3 (cumulative dose) mmol/kg gadoteridol (Gd HP-DO3A; ProHance) in all animals. The film images were interpreted in a prospective fashion by a single neuroradiologist who was masked to imaging technique and contrast dosing. The digital data was analyzed by region of interest measurement. At the end of the imaging studies, the animals were sacrificed and the epidural lesion confirmed by gross and microscopic exam.

RESULTS

On a prospective masked read of the MR films, epidural tumor was depicted best on postcontrast fat saturation T1-weighted scans using a cumulative contrast dose of 0.3 mmol/kg. Substantial contrast enhancement of the tumor was observed in all instances on postcontrast scans. The precontrast T1-weighted scan was least efficacious for lesion identification and differentiation from the compressed spinal cord. Depending on the pulse sequence used, one (T2-weighted) to three (T1-weighted without fat saturation) of the lesions could not be identified prospectively on precontrast scans. Lesion growth with time after implantation was chronicled by MR imaging, accompanied by progression of symptoms. On region of interest analysis, differentiation of epidural tumor from normal cord was greatest (11.6 +/- 6.1) on postcontrast scans using a cumulative contrast dose of 0.3 mmol/kg. The level of differentiation achieved was twice that of postcontrast scans using a contrast dose of 0.1 mmol/kg (5.9 +/- 3.6). These results were superior on statistical analysis to that with all other scan techniques (P = 0.002-0.0005). Cord and tumor could not be differentiated on the basis of signal intensity, with any statistical significance, using precontrast T1 and T2 scans. The lesions were confirmed in each animal by gross and microscopic exam. On inspection of the gross specimen, the tumors were noted to be located in the epidural space and to cause cord compression. On microscopic exam, the tumor was composed of epithelial cells that were moderately pleomorphic.

CONCLUSIONS

In the New Zealand White rabbit, an epidural tumor could be created consistently using the described percutaneous approach. These lesions are suitable for MR imaging studies, examining lesion detectability and efficacy of imaging technique. The lesions created in the current study could not be diagnosed prospectively in all cases on precontrast T1 and T2 scans images. Postcontrast scans were most efficacious for diagnosis and lesion delineation, with high-dose (0.3 mmol/kg) scans superior to standard dose (0.1 mmol/kg).

Detectability of small liver metastases with gadolinium BOPTA

RATIONALE AND OBJECTIVES

The ability to detect small liver metastases was evaluated with both gadolinium Gd BOPTA and Gd HP-DO3A on high-field (1.5 tesla [T]) magnetic resonance (MR) imaging using a rabbit tumor model.

METHODS

Five New Zealand White rabbits with metastatic liver disease (VX-2 adenocarcinoma) were imaged on a 1.5 T Siemens Vision MR system. Magnetic resonance studies were obtained in each animal on days 8 and 9 after tumor implantation. Each animal was studied twice, once after injection of 0.3 mmol/kg Gd HP-DO3A (gadoteridol or ProHance) and once after injection of 0.1 mmol/kg Gd BOPTA (gadobenate dimeglumine or MultiHance). The order of injection for the two agents was randomized with the two studies in any one animal separated by 24 hours to allow for clearance. Magnetic resonance image acquisition was performed in all cases with suspended respiration. Baseline two-dimensional FLASH T1-weighted and turbo-spin echo T2-weighted scans were acquired first. The contrast was then administered as an intravenous bolus. T1-weighted scans were acquired at 1, 5, 15, 30, 45, and 60 minutes after administration of Gd BOPTA and 1, 5, and 15 minutes after administration of Gd HP-DO3A. Each rabbit was killed after completion of imaging, their liver removed and taken to the veterinarian at the University's animal disease diagnostic laboratory for lesion confirmation.

RESULTS

Despite acquisition of precontrast T2-weighted scans, lesions could not be identified with certainty in four of five animals in the Gd HP-DO3A study. Normal liver signal intensity increased from 895 +/- 17 to a peak of 1384 +/- 50 at 1 minute after Gd HP-DO3A administration. After Gd BOPTA administration, normal liver signal intensity increased from 899 +/- 105 to a peak of 1433 +/- 76 at 15 minutes. Liver enhancement thereafter decreased gradually to 1297 +/- 84 at 60 minutes. The injection of 0.3 mmol/kg Gd HP-DO3A resulted in parenchymal enhancement, which was statistically superior (P < 0.01) to an injection of 0.1 mmol/kg Gd BOPTA at 1 minute, not statistically different at 5 minutes, and inferior (P < 0.02) at 15 minutes. From region of interest measurements, lesion detectability was statistically superior on scans at 15 to 60 minutes after Gd BOPTA administration compared with precontrast T1- and T2-weighted scans (P values: < 0.03- < 0.005). Lesion detectability was maximum at 30 minutes postcontrast (15.2 +/- 4.5), markedly superior to that precontrast on both T1- (5.7 +/- 5.0) and T2-weighted scans (7.2 +/- 1.5). On masked film review of the Gd BOPTA case set, no lesions were noted prospectively on T2-weighted scans. Lesions in all five animals were well visualized on scans 45 to 60 minutes after Gd BOPTA administration. The Gd HP-DO3A case set was not read masked, as lesions could be identified only in one of the five animals with all films available for inspection. An additional feature of scans with Gd BOPTA (used at a dose of 0.1 mmol/kg), in distinction to those with Gd HP-DO3A (used at a dose of 0.3 mmol/kg), was the diminished enhancement of hepatic vessels.

CONCLUSIONS

Using a rabbit model, small metastatic lesions (diameter, 2-4 mm) were well visualized on delayed postcontrast Gd BOPTA scans. These lesions could not be diagnosed prospectively on T2-weighted images. In only one of five animals were lesions detected on early dynamic post-contrast high-dose Gd HP-DO3A scans.

Spontaneous pneumoperitoneum and other nonsurgical causes of intraperitoneal free gas

Intraperitoneal free gas seen radiologically as air under the diaphragm nearly always indicates a perforated abdominal viscus that requires surgical intervention. Rarely, however, the presence of a pneumoperitoneum may not indicate an intra-abdominal perforation and thus may not require laparotomy. Such a situation is termed spontaneous or nonsurgical pneumoperitoneum. In this review, we explore the aetiological mechanisms and the pathophysiology of the appearance of intra-abdominal free gas. An appreciation of the condition and its likely aetiological factors should improve awareness and possibly reduce the imperative to perform an emergency laparotomy on an otherwise well patient with an unexplained pneumoperitoneum.

Immunohistochemical analysis of the proapoptotic protein Par-4 in normal rat tissues

Prostate apoptosis response 4 (par-4) is a recently identified gene that encodes a transcription factor, Par-4, with a leucine zipper domain. Par-4 protein is constitutively expressed in various cell lines and is functionally required but not sufficient for apoptosis. Induction of Par-4 in cultured cells is found exclusively during apoptosis, and ectopic overexpression of Par-4 enhances the potency of apoptotic stimuli. Western or Northern blot analysis on mRNA or protein extracts, respectively, from rat organs revealed that the expression of Par-4 was ubiquitous and was not restricted to any specific organ(s). To further identify specific cell types that expressed Par-4, we performed an immunohistochemical analysis of the protein in paraffin-embedded sections of various organs from rats. Our findings indicated that consistent with its proapoptotic role, Par-4 is expressed in apoptotic granulosa cells of atretic ovarian follicles and in terminally differentiated cells, such as the cardiomyocytes, cerebellar Purkinje cells, and pyramidal cells of the hypothalamus. Moreover, testosterone ablation by castration of rats caused an early and transient induction of Par-4 in the ductal cells of the prostate that undergo apoptosis. By contrast, in tissues in which the cells could be visually differentiated from their mature counterparts, Par-4 expression was lowest in the mature cells. This was the case for epithelia of the mammary and the prostate gland in which the basal cells maintained higher protein levels of Par-4 than did the terminally differentiated ductal cells. Similarly, cells of the stratum corneum of the skin and cells on top of the duodenal villi stained less intensely for Par-4 as compared to the stem cells in the stratum basale and at the bottom of the crypts of Lieberkühn, respectively. It is possible that Par-4 has to be down-regulated for successful differentiation in these tissues. Taken together, the widespread expression of Par-4 in various adult cell types underscores the physiological importance of the protein. The observation of constitutive Par-4 expression in the stem cell compartments is inconsistent with the probability of apoptosis per se and can be extended to determine whether Par-4 plays a role in other cellular processes.

Multiple abortions associated with caprine herpesvirus infection in a goat herd

Herpesvirus infection of pregnant goats may result in abortion of fetuses without other signs of infection in does. Fetuses aborted as a result of caprine herpesvirus infection have tissue necrosis and intranuclear inclusion bodies in multiple organs.

Association between schizophrenia and a microsatellite polymorphism at the dopamine D5 receptor gene

An association study of 97 patients with DSM-III-R schizophrenia and 97 matched controls was performed using a polymorphic microsatellite repeat at the dopamine D5 receptor gene. We observed a significant difference between the allele frequencies of patients and controls (chi 2 = 23.4, df = 12, p = 0.019). This reflects an excess of allele 4 (140 bp) in the patients when compared with the control sample (chi 2 = 7.087, p < 0.01; odds ratio = 2.98, 95% CI 1.29-6.86). However, this association remains tentative until confirmation in other samples.

Linkage study of chromosome 6p in sib-pairs with schizophrenia

Following reports of linkage between schizophrenia and markers in the chromosomal region 6p24-22 we have studied nine microsatellite markers spanning 40 cM of this region in our sample of 102 affected sibling pairs from 86 families. Allele sharing identity by descent was examined using likelihood based sib-pair analysis as implemented by the program SPLINK. No evidence for linkage was obtained and the highest lod score was only 0.192 for D6S309. We conclude that if there is a susceptibility locus for schizophrenia in this region then its effect size is so small as to render our study insufficiently powerful to detect it.

Renal metastasis. Detection and characterization on enhanced magnetic resonance imaging using an animal model

RATIONALE AND OBJECTIVES

A new animal model was developed in rabbits (renal metastasis using the VX-2 tumor line), and magnetic resonance (MR) imaging performed before and after intravenous gadoteridol injection to assess lesion conspicuity and characterization.

METHODS

Six New Zealand White rabbits with renal metastases were studied on a 1.5-tesla Siemens Vision MR unit. Iodinated contrast was given intravenously to the rabbits, before implantation, to visualize the kidneys under fluoroscopy. Using a 5/8-inch 25-gauge needle, 0.1 mL of minced, screened VX-2 tumor was injected percutaneously into each kidney at the corticomedullary junction. Animals were studied on day 7 after implantation. Baseline fast low-angle shot (FLASH) T1-weighted and fast spin echo T2-weighted breathhold scans were first obtained. Then, an additional precontrast turbo-FLASH T1-weighted scan was acquired. After these scans, 0.1 mmol/kg gadoteridol (gadolinium HP-D03A; ProHance) was injected intravenously at a rate of 1.5 mL/second. Dynamic breathhold turbo-FLASH T1 images were then obtained at 0, 6, 12, 19, 25, and 31 seconds after injection and at 1, 2, and 10 minutes after injection. The T1 multislice FLASH two-dimensional scan was repeated at 10 minutes after contrast. Imaging results were analyzed by region of interest measurement and correlated with tissue pathology.

RESULTS

On dynamic T1-weighted turbo-FLASH scans, lesion conspicuity, specifically (SI(kidney)-SI(tumor)/noise), increased from 7 +/- 7 signal intensity precontrast to a maximum of 14 +/- 8 at 1 minute after contrast. This increase was statistically significant (P = 0.002). An initial rapid increase in tumor conspicuity occurred within the first 30 seconds after contrast, with the curve flattening thereafter. Lesion conspicuity on the precontrast T2-weighted scans was 9 +/- 10, not statistically different from results with either of the precontrast T1-weighted scan techniques. Using T1-weighted FLASH technique, lesion conspicuity increased from 10 +/- 5 precontrast to 31 +/- 12 postcontrast. As with turbo-FLASH, the improvement in tumor conspicuity after contrast on FLASH scans was statistically significant (P = 0.02). The difference between postcontrast FLASH scans and precontrast T2-weighted scans also was statistically significant, with postcontrast scans superior for lesion conspicuity (P = 0.01). Each tumor was confirmed on pathologic exam.

CONCLUSIONS

This research establishes a model of metastasis to the kidney for use in imaging studies. The conspicuity of a small renal metastasis is shown to be improved on early dynamic imaging, as well as at 10 minutes after intravenous injection of 0.1 mmol/kg gadoteridol. Observation of dynamic signal intensity changes provides additional information regarding lesion characterization, supplementing that from precontrast scans.

Successful management of external duodenal fistula in a specialized unit

BACKGROUND

High-output external duodenal fistula remains a challenging condition to treat. Despite advances in metabolic and nutritional care, mortality rates remain high.

METHOD

Retrospective casenote review of patients managed on a specialised unit.

RESULTS

Thirteen of 388 admissions (3.4%, 11 males, median age 51 years) had an external duodenal fistula. Management was by eradication of abdominal and systemic sepsis and maintenance of nutritional status by the administration of total parenteral nutrition. The majority of fistulas followed surgery for peptic ulcer disease. Eight of 13 fistulas closed spontaneously, and of those requiring operative closure, surgery was successful in 4 of 5 cases. There were 2 mortalities.

CONCLUSION

High-output external duodenal fistula may be successfully managed in a specialised unit.

No evidence for an allelic association between schizophrenia and markers D22S278 and D22S283

We report a case control association study using markers D22S278 and D22S283 in 90 unrelated patients with DSMIII-R schizophrenia and 90 controls matched for ethnicity, age and sex. No differences between allele frequencies for either marker were observed when the two groups were compared (D22S278: chi 2 = 6.53, df = 7, P = 0.51; D22S283: chi 2 = 14.73, df = 15, P = 0.48). These findings fail to support previous work by others suggesting the presence of allelic association between the markers D22S278 and D22S283 and schizophrenia.

Experimental induction of equine protozoal myeloencephalitis in horses using Sarcocystis sp. sporocysts from the opossum (Didelphis virginiana)

Sarcocystis sp. sporocysts isolated from eight feral opossums (Didelphis virginiana) were pooled and fed to 18 commercially reared budgerigars (Melopsittacus undulatus), 14 wild-caught sparrows (Passer domesticus), one wild-caught slate-colored Junco (Junco hyemalis) and five weanling horses (Equus caballus). All budgerigars died within 5 weeks post inoculation (wpi). Histologic examination revealed meronts within the pulmonary epithelia and typical Sarcocystis falcatula sarcocysts developing in the leg muscles. Sparrows were euthanized 13 and 17 wpi and their carcasses were fed to four laboratory raised opossums. Sporocysts were detected in the feces of two opossums on 15 days post inoculation (dpi) and in a third opossum on 40 dpi. Fecal samples from the fourth opossum remained negative; however, sporocysts were found in intestinal digests from all four opossums. Sporocysts were not found in feces or intestinal digest of an additional opossum that was fed three uninoculated sparrows. Five foals were fed sporocysts (Foals 2, 3, 4, 5, and 7) and two foals were maintained as uninoculated controls (Foals 1 and 6). Sporocysts from two additional feral opossums also were fed to foals. Foal 5 was given 0.05 mg kg-1 dexamethasone sodium phosphate daily beginning 2 days before inoculation for a total of 2 weeks. Horse sera were tested three times per week, and cerebrospinal fluid (CSF) samples were tested biweekly for anti-Sarcocystis neurona antibodies by Western blot analysis. No foals had any S. neurona-specific antibodies by Western blot analysis prior to sporocysts ingestion. Seroconversion occurred in Foals 3, 5, and 7 by 24 dpi, followed by positive CSF tests on 28 dpi. Foals 2 and 4 seroconverted by 40 dpi. Cerebrospinal fluid from Foal 2 tested positive by 42 dpi, but Foal 4 remained seronegative throughout the study. Sera and CSF from control Foals 1 and 6 remained seronegative. All foals with positive CSF developed neurologic clinical signs. Neurologic disease was evident in Foals 2 and 3 by 42 dpi and in Foal 7 by 28 dpi. The severity of clinical signs progressed to marked spasticity, hypermetria and ataxia in Foal 7 by the end of the trial. Necropsy examination of inoculated foals did not reveal gross lesions; however, microscopic lesions consistent with equine protozoal myeloencephalitis (EPM) were found in Foals 2, 3, and 7. Protozoa were not observed in the tissue sections. Microscopic lesions consistent with EPM were not found in Foals 4 and 5 or in uninoculated control Foals 1 and 6. Foal 5 had unilateral non-inflammatory lesions in the cervical and thoracic spinal cord consistent with cord compression. These data indicate that the opossum is a definitive host of S. neurona.

Hepatic abscesses. Magnetic resonance imaging findings using gadolinium-BOPTA

RATIONALE AND OBJECTIVES

Gadolinium (Gd)-BOPTA was evaluated in a rabbit liver abscess model and compared with Gd-HP-DO3A, examining lesion conspicuity and characterization.

METHODS

Five New Zealand White rabbits with a liver abscess were studied on a 1.5-tesla Siemens Vision magnetic resonance unit. The disease model was created by surgically implanting a gel capsule filled with fusobacterium into the central or left lobe of the liver. For imaging, the animals were ventilated using a Harvard pump. Pancuronium bromide (0.12 mg/kg) was administered to allow acquisition of breath-hold scans. Magnetic resonance scans were obtained in each animal on days 2 and 3 after surgery. Every animal was studied twice, once after intravenous injection of 0.3 mmol/kg Gd-HP-DO3A (gadoteridol; ProHance) and once after intravenous injection of 0.1 mmol/kg Gd-BOPTA (gadobenate dimeglumine; MultiHance). The order of injection for the two agents was randomized with the two studies in each animal, separated by 24 hours to permit clearance. Image acquisition was performed in each instance with respiration suspended. Baseline two-dimensional spin-echo T1-weighted and fast spin-echo T2-weighted breath-hold scans were obtained first. The voxel dimensions were 5 x 0.8 x 0.8 mm3. Imaging times were 23 seconds for the T1-weighted scan and 26 seconds for the T2-weighted scan. Postcontrast scans, using spin-echo T1-weighted technique, were obtained at 1, 3, 5, and 15 minutes after contrast injection, whether Gd-HP-DO3A or Gd-BOPTA was used. Additional scans were obtained at 30, 45, and 60 minutes after Gd-BOPTA administration. At the completion of imaging on day 3, each animal was killed and the liver was removed and taken to a veterinary pathologist at the University's animal disease diagnostic lab for gross and histologic examination.

RESULTS

The enhancement of normal liver parenchyma, assessed by region of interest measurement and specifically as (SI(t) - SI0)/SI0 x 100, peaked at 119 +/- 37% 1 minute after injection of 0.3 mmol/kg Gd-HP-DO3A and at 126 +/- 30% 30 minutes after injection of 0.1 mmol/kg Gd-BOPTA. The difference in enhancement achieved, comparing results at each time point, was statistically significant only at 1 and 3 minutes postcontrast (P = 0.003 and 0.03). Lesion conspicuity, specifically (SIliver - SIlesion/noise), increased from 272 +/- 29 precontrast to a maximum of 639 +/- 73 at 30 minutes postcontrast using a dose of 0.1 mmol/kg Gd-BOPTA, with the improvement statistically significant (P = 0.0003). Lesion conspicuity on the T2-weighted scan was 137 +/- , with the Gd-BOPTA scan markedly superior (P = 0.00004). On scans at 45 and 60 minutes after Gd-BOPTA administration, a progressive increase in signal intensity in the central necrotic portion of the lesion was observed. This was most consistent with gradual diffusion of the agent from the adjacent liver into the lesion. Using Gd-HP-DO3A at 0.3 mmol/kg (three times the dose for Gd-BOPTA), lesion conspicuity increase from 305 +/- 37 precontrast to a maximum of 701 +/- 92 at 1 minute postcontrast, with this difference also statistically significant (P = 0.0004). The abscess rim exhibited moderate contrast enhancement, greater than that of normal liver parenchyma, on early postcontrast images with Gd-HP-DO3A.

CONCLUSIONS

The conspicuity of an early liver abscess is improved markedly on delayed imaging after administration of 0.1 mmol/kg Gd-BOPTA. Although a similar magnitude of parenchymal enhancement can be obtained after the administration of an extracellular agent, such as Gd-HP-DO3A, high-contrast dose (0.3 mmol/kg) and early dynamic imaging are required. The appearance of a liver abscess on late scans (45 to 60 minutes) after Gd-BOPTA injection is distinct from that of nonnecrotic metastases, with diffusion of the agent into the lesion noted.

Early dynamic magnetic resonance imaging of liver metastases with 0.3 and 0.6 mmol/kg gadoteridol injection

RATIONALE AND OBJECTIVES

The potential for improvement in liver-lesion conspicuity on early dynamic scans after bolus intravenous gadolinium (Gd) chelate administration was evaluated using gadoteridol (Gd-HP-DO3A; Prohance) at doses of 0.3 and 0.6 mmol/kg.

METHODS

Five New Zealand white rabbits with focal VX-2 adenocarcinoma liver metastases were studied on a 1.5-tesla Siemens Vision scanner. Each rabbit was imaged twice (on two separate days), after injections of 0.3 mmol/kg and 0.6 mmol/ kg Gd-HP-DO3A. The contrast dose (0.3 or 0.6 mmol/kg) was given as a single intravenous injection. The order of injection for the two doses was randomized, with the two studies (in any one rabbit) separated by 24 hours to allow for clearance. Contrast was administered using an autoinjector at a rate of 1.5 mL/second. Turbo-fast low-angle shot scans were obtained before and at 6, 12, 19, 25, 31, 60, 120, 180, 240, 300, and 600 seconds after contrast injection. The lesions were confirmed, after killing the rabbit, by gross and microscopic examination.

RESULTS

The enhancement of normal liver parenchyma, assessed by (SIt-SIo)/SIo.100, (SI = signal intensity) peaked at 32% +/- 4% 19 seconds after injection of 0.3 mmol/kg and at 38% +/- 5% 31 seconds after injection of 0.6 mmol/kg. The difference in maximum parenchymal enhancement achieved, comparing the 0.3 and 0.6 mmol/kg doses, was statistically significant (P < 0.03). Lesion conspicuity, specifically (SIliver-SIlesion/noise), increased from 4.5 +/- 2.3 precontrast to a maximum of 6.8 +/- 1.2 at 19 seconds postcontrast using a dose of 0.3 mmol/kg, with the difference statistically significant (P < 0.03). The increase with a dose of 0.6 mmol/kg was from 4.2 +/- 0.7 to 6.5 +/- 1.9 with this difference also statistically significant (P < 0.02). There was no statistically significant difference in lesion conspicuity between the doses of 0.3 and 0.6 mmol/kg.

CONCLUSIONS

Conspicuity of liver metastases can be improved substantially with dynamic magnetic resonance imaging and rapid intravenous bolus contrast injection with a dose of 0.3 mmol/kg. No further improvement is noted at a dose of 0.6 mmol/kg, despite greater positive contrast enhancement of normal liver parenchyma.

The use of gadolinium-BOPTA on magnetic resonance imaging in brain infection

RATIONALE AND OBJECTIVES

The use of gadolinium (Gd)-BOPTA as a magnetic resonance contrast agent for central nervous system disease was studied in a canine brain abscess model.

METHODS

A Streptococcus faecalis brain abscess was evaluated in five dogs at 1.5T. Imaging was performed during the late cerebritis stage, at 5 to 7 days after surgery. Magnetic resonance scans were acquired before and at 1, 5, 15, 30, 45, and 60 minutes after contrast administration, using a dose of 0.1 mmol/kg. Scans also were acquired both before and after contrast injection with the implementation of magnetization transfer.

RESULTS

Lesion enhancement, quantified by region-of-interest measurement, peaked at 5 minutes after contrast injection. Both the increase in lesion enhancement from 1 to 5 minutes after injection and the decrease from 5 to 15 minutes after injection, although small, were statistically significant (P < 0.004 and P < 0.03, respectively). The application of magnetization transfer improved lesion enhancement, as measured by signal difference/noise, by 39%. This result also was statistically significant (P < 0.001).

CONCLUSIONS

In intraparenchymal brain infection, Gd-BOPTA provides effective lesion enhancement when used at a dose of 0.1 mmol/kg. Further research is needed to compare the magnitude of enhancement achieved with Gd-BOPTA, which has weak protein binding and both hepatobiliary and renal excretion, with that with Gd chelates, which have pure renal excretion.

No evidence for allelic association between schizophrenia and a polymorphism determining high or low catechol O-methyltransferase activity

OBJECTIVE

Catechol O-methyltransferase (COMT) inactivates catecholamines by methylating their m-hydroxy group. Some previous studies using biochemical methods have found higher levels of COMT activity in schizophrenic patients. Recently, the genetic polymorphism that underlies variation in COMT activity, which results in the creation of a NlaIII restriction site in the low-activity allele, has been elucidated.

METHOD

This study investigated this polymorphism in 78 unrelated schizophrenic patients and 78 comparison subjects matched for age and ethnicity. High-molecular-weight DNA was isolated from lymphocytes with routine procedures, and each individual was typed for high and low COMT activity.

RESULTS

The frequency of the NlaIII polymorphism was 0.51 in the schizophrenic patients and 0.53 in the comparison subjects, and no significant allelic or genotypic associations were observed.

CONCLUSIONS

There was no evidence for variation in COMT activity between a group of schizophrenic patients and matched comparison subjects.

Evaluation of gadolinium 2,5-BPA-DO3A, a new macrocyclic hepatobiliary chelate, in normal liver and metastatic disease on high field magnetic resonance imaging

RATIONALE AND OBJECTIVES

A new hepatobiliary gadolinium chelate, gadolinium (Gd) 2,5-BPA-DO3A, was compared in two animal species with Gd HP-DO3A (gadoteridol), a clinically approved extracellular contrast agent, and Gd Cy2-DOTA, a second hepatobiliary chelate in preclinical development. The ligand in Gd 2,5-BPA-DO3A is macrocyclic in nature, as opposed to the linear structure of Gd DTPA. Gadolinium 2,5-BPA-DO3A was evaluated on magnetic resonance imaging at 1.5 T, examining specifically liver parenchymal enhancement and lesion delineation, the latter in metastatic disease.

METHODS

Gadolinium 2,5-BPA-DO3A was evaluated in five normal rhesus monkeys and four New Zealand White rabbits with implanted VX-2 liver tumors. These studies were compared with magnetic resonance exams in the same animals using Gd HP-DO3A and Gd Cy2-DOTA. A contrast dose of 0.1 mmol/kg intravenous was employed in each instance, with the sequence of administration (for the three agents) randomized and at least 72 hours between injections. Spin echo breathhold T1-weighted scans were obtained before and at multiple times after contrast administration. Postcontrast scans were acquired from 1 to 60 minutes after injection in the monkeys and from 1 to 240 minutes in the rabbits.

RESULTS

Enhancement of normal liver parenchyma was markedly superior with Gd 2,5-BPA-DO3A compared with Gd HP-DO3A and Gd Cy2-DOTA in both monkeys and rabbits. At 2 and 60 minutes after contrast administration, the liver signal intensity in the monkey was 452 +/- 56 and 440 +/- 69 with Gd 2,5-BPA-DO3A compared with 295 +/- 34 and 256 +/- 38 with Gd HP-DO3A. The difference between agents was statistically significant at all postcontrast time points in the rhesus monkey. Excretion of contrast into the gall bladder was consistently observed after Gd 2,5-BPA-DO3A injection in both animal species. Maximum lesion conspicuity occurred in the rabbit at 45 minutes after Gd 2,5-BPA-DO3A administration. At 45 minutes postinjection, liver-lesion contrast was 0.60 +/- 0.15 with Gd 2,5-BPA-DO3A, 0.35 +/- 0.11 with Gd Cy2-DOTA, and 0.12 +/- 0.04 with Gd HP-DO3A, with the differences between agents being statistically significant.

CONCLUSIONS

Gadolinium 2,5-BPA-DO3A is superior to both Gd Cy2-DOTA and Gd HP-DO3A in the degree of enhancement of normal liver parenchyma achieved after intravenous injection. This leads to improved liver lesion delineation with Gd 2,5-BPA-DO3A on delayed postcontrast magnetic resonance scans.