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Biomedical subjects

H J Williams

Publications and source records attributed to H J Williams.

At least 19 recordsLinked to original sources
PubMed2006

Nest liquid resources of several cavity nesting bees in the genus Centris and the identification of a preservative, levulinic acid.

Twig-nesting species of bees in the genus Centris including C. bicornuta, C. analis, C. vittata, and C. nitida, found in the dry forest of Guanacaste Province of Costa Rica, provision their nests with pollen and nectar, rather than pollen and oil as reported for other Centris species. The liquid contents of the nests of these four species were found to contain sugars including 66-75% fructose, 25-33% glucose, and a trace of sucrose. The sugar concentration averaged 47.2%, slightly higher than most flower nectars. No tri-, di-, or monoglycerides, the main components of the flower oil of Byrsonima crassifolia, were detected in the nest provisions. Although these four Centris species are also known to collect oil from B. crassifolia, the oil appears to be used for activities other than nest provisioning. The liquid nest contents did have a slight goat-like odor, suggesting the presence of short-chain fatty acids, and were found to contain a small amount (less than 1%) of three fatty acids. Two of these, butanoic and octanoic acid, were found in trace amounts and are responsible for the goat-like odor. A third was identified as levulinic acid, which made up about 99% of the nest fatty acid contents. This fatty acid had little odor, but may be important as a fungicidal agent. Attempts to determine the source of the fatty acids, were not successful.

Animals↗
PubMed2005

The effect of X-rays on bone: a pictorial review.

The deleterious effects of X-rays on bone have been recognised for almost a century and continue to be seen today because of improved survival in patients treated for malignancy with radiotherapy with or without other treatments. In this pictorial review we present the imaging features of radiation damage to bone highlighting the differences seen in the immature skeleton and post-skeletal fusion. In the former, damage is greatest to the physis resulting in growth disturbances. In the mature skeleton there is a spectrum of changes from mild osteopenia, through disordered attempts at healing with varying degrees of sclerosis, radionecrosis which may lead to acute fractures following minimal trauma and insufficiency fractures both with refractory healing to the dreaded complication of sarcomatous transformation. The imaging appearances are illustrated and the features that help distinguish malignant change from other complications stressed.

Bone Diseases, Developmental↗
PubMed2004

Imaging features of intraosseous ganglia: a report of 45 cases.

The aim of this study is to report the spectrum of imaging findings of intraosseous ganglia (IG) with particular emphasis on the radiographic and magnetic resonance (MR) features. Forty-five patients with a final diagnosis of IG were referred to a specialist orthopaedic oncology service with the presumptive diagnosis of either a primary or secondary bone tumour. The diagnosis was established by histology in 25 cases. In the remainder, the imaging features were considered characteristic and the lesion was stable on follow-up radiographic examination. Radiographs were available for retrospective review in all cases and MR imaging in 29. There was a minor male preponderance with a wide adult age range. Three quarters were found in relation to the weight-bearing long bones of the lower limb, particularly round the knee. On radiographs all were juxta-articular and osteolytic; 74% were eccentric in location, 80% had a sclerotic endosteal margin and 60% of cases showed a degree of trabeculation. Periosteal new bone formation and matrix mineralization were not present. Of the 29 cases that underwent MR imaging, 66% were multiloculated. On T1-weighted images the IG contents were isointense or mildly hypointense in 90% cases. Forty-one per cent of the cases showed a slightly hyperintense rim lining that enhanced with a gadolinium chelate. Thirty-eight per cent were associated with soft tissue extension and 17% with a defect of the adjacent articular cortex. Fifty-five per cent showed surrounding marrow oedema on T2-weighted or STIR images and two cases (7%) a fluid-fluid level prior to any surgical intervention. The authors contend that it is semantics to differentiate between an IG and a degenerate subchondral cyst as, while the initial pathogenesis may vary, the histological endpoint is identical, as are the imaging features apart from the degree of associated degenerative joint disease. IGs, particularly when large, may be mistaken for a bone tumour. Correlation of the typical radiographic and MR imaging features will indicate the correct diagnosis and obviate the need for biopsy.

Adult↗
PubMed2004

Bone within a bone.

The "bone within a bone" appearance is a well-recognized radiological term with a variety of causes. It is important to recognize this appearance and also to be aware of the differential diagnosis. A number of common conditions infrequently cause this appearance. Other causes are rare and some remain primarily of historical interest, as they are no longer encountered in clinical practice. In this review we illustrate some of the conditions that can give the bone within a bone appearance and discuss the physiological and pathological aetiology of each where known.

Anemia, Sickle Cell↗
PubMed2003

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.

Adult↗
PubMed2003

Detailed analysis of PRODH and PsPRODH reveals no association with schizophrenia.

People with deletion of the chromosome 22q11 region associated with velo cardio-facial syndrome (VCFS) have a remarkably high risk of developing schizophrenia. Recently, the gene proline dehydrogenase (PRODH) which maps to 22q11 and is also an excellent functional candidate gene for psychosis, has been reported to show genetic association with schizophrenia. We have screened all the exons and adjacent intronic sequences of PRODH for the presence of sequence variation in 14 DSM IV schizophrenic subjects. Similarly, we also screened all putative exons of a sequence that is similar to proline dehydrogenase (PsPRODH) and which also maps within the deleted region. A total of nine single nucleotide polymorphisms (SNPs) were identified in PRODH, eight of which were exonic, while in PsPRODH, five SNPs were identified, one of which was in a putative exon. All samples were tested for association in a pooled sample of 368 DSM IV diagnosed schizophrenic subjects and 368 matched controls. None of the variants identified in PRODH gave even modest evidence for allelic association (P < 0.1). In PsPRODH, two variants (-3864G > A and 226G > A) gave P values < 0.1. These were individually genotyped in the same subjects that had been used to construct the pools. Although a trend for association was confirmed, neither showed evidence for association at the P </= 0.05 level. These results do not suggest that PRODH or PsPRODH contribute to the aetiology of schizophrenia, and that the putative schizophrenia susceptibility gene in 22q11 remains unknown.

Adult↗
PubMed2003

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.

Adult↗
PubMed2003

Chromosome 22q11 deletions, velo-cardio-facial syndrome and early-onset psychosis. Molecular genetic study.

BACKGROUND: Velo-cardio-facial syndrome (VCFS) is associated with interstitial deletions of chromosome 22q11. About 30% of patients with VCFS have psychosis, and the rate of these deletions in schizophrenia has been reported to be about 1%. Even higher rates of VCFS deletions have been reported for childhood-onset schizophrenia. AIMS: To test the hypothesis that there is an increased rate of VCFS among patients with early-onset psychosis (age at onset <18 years). We screened 192 early-onset patients and 329 patients with adult-onset schizophrenia. METHOD: We genotyped the patients and 444 healthy controls for hemizygosity of five microsatellite markers and one single nucleotide polymorphism that map to the 22q11-deleted region. RESULTS: One patient had a VCFS deletion, confirmed with semi-quantitative polymerase chain reaction. None of the controls showed a pattern of genotypes consistent with hemizygosity. CONCLUSIONS: VCFS may be less frequent among patients with psychosis than previously suggested; this rate is not increased among early-onset patients.

Abnormalities, Multiple↗
PubMed2003

Imaging of paediatric mediastinal abnormalities.

The mediastinum in children can be a difficult area to assess on the chest radiograph: even the normal thymus can give the impression of a mediastinal mass lesion. When there is suspicion of a mediastinal mass, its location within the mediastinum helps to limit the differential diagnosis. Further imaging with ultrasound, computed tomography and magnetic resonance imaging helps to characterise the lesion, define its extent and detect complications. Abnormal mediastinal contours may also be caused by congenital anomalies of the mediastinal vessels, which can be demonstrated non-invasively using magnetic resonance imaging. The main purpose of this article is to review the anatomy of the mediastinum and imaging of mediastinal mass lesions in children together with some vascular anomalies that can simulate a mediastinal mass.

Child↗
PubMed2002

Screening the human protocadherin 8 (PCDH8) gene in schizophrenia.

Abnormalities in synaptic connectivity and plasticity have been implicated in the pathophysiology of schizophrenia. Molecules involved in the development and maintenance of neural circuitry include the recently cloned protocadherins. Human protocadherin 8 (PCDH8) is homologous to 'arcadlin', a molecule shown to play a role in hippocampal synaptic function in the rat. The gene encoding PCDH8 maps to a region on chromosome 13 where linkage to schizophrenia has been reported. In this study, the entire expressed sequence of the PCDH8 gene and over 800 bp of the 5' flanking region were screened for polymorphisms in 30 DSM-IV schizophrenia individuals using Denaturing High Performance Liquid Chromatography (DHPLC). A total of nine single nucleotide polymorphisms were identified, including three in the first exon that are predicted to change the amino acid sequence. One polymorphism, causing the Trp7Arg change in the putative signal peptide, showed a trend towards excess of the arginine encoding allele in a case-control sample consisting of 520 DSM-IV schizophrenia patients and 535 matched controls from the UK (chi2=3.72, P [1 df]= 0.054). However, this polymorphism did not show preferential transmission to schizophrenic individuals in a separate sample of 203 proband-parent trios from Bulgaria. A second, rare single nucleotide variation, predicting the non-conservative amino acid change Glu39Ala, was found in one schizophrenic individual and their affected sibling but not in a further 352 affected individuals, nor 357 controls. These results suggest that any contribution of PCDH8 polymorphisms to schizophrenia susceptibility is likely to be weak, although the existence of rare variations of stronger effect cannot be excluded.

Adult↗
PubMed2002

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.

Base Sequence↗
PubMed2002

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).

Chromosome Deletion↗
PubMed2002

Imaging features of breast trauma: a pictorial review.

Accidental injury to the female breast can cause symptoms and signs which may mimic carcinoma and can also be painful or disfiguring. Nine women who sustained injury to the breast are presented, illustrating some of the manifestations of traumatic injury to the female breast, the majority of which are attributable to fat necrosis. A brief discussion of the clinical and imaging features of fat necrosis is included. These cases reinforce the importance of triple assessment in any woman presenting with a breast lump, even with a clear history of trauma.

Journal Article↗
PubMed2002

Imaging of congenital cystic lung lesions.

Congenital cystic lung lesions are a rare but clinically significant group of anomalies, including congenital cystic adenomatoid malformation (CCAM), pulmonary sequestration, congenital lobar emphysema (CLE) and bronchogenic cysts. These conditions can all present on imaging studies as air or fluid filled cysts. Widespread use of antenatal ultrasound has led to increased detection of infants with congenital thoracic abnormalities in utero, resulting in a better understanding of the natural history of many of these lesions and also allowing provision to be made for delivery and postnatal management. More recently antenatal magnetic resonance (MR) imaging has provided further information on the nature of many of these lesions and helped to differentiate them from extrathoracic abnormalities such as congenital diaphragmatic hernia (CDH), which is important in parental counselling. Many children with congenital cystic lung lesions will present with symptoms resulting in the need for prompt diagnosis and treatment and imaging has an essential role in the management of these children. Some congenital lung lesions are treated surgically, whilst others are managed conservatively.

Bronchogenic Cyst↗