Showing papers by "John Radcliffe Hospital published in 1987"

HLA-DQ beta gene contributes to susceptibility and resistance to insulin-dependent diabetes mellitus.

Abstract: Over half of the inherited predisposition to insulin-dependent diabetes mellitus maps to the region of chromosome 6 that contains the highly polymorphic HLA class II genes which determine immune responsiveness. Analysis of DNA sequences from diabetics indicates that alleles of HLA-DQ beta determine both disease susceptibility and resistance, and that the structure of the DQ molecule, in particular residue 57 of the beta-chain, specifies the autoimmune response against the insulin-producing islet cells.

HLA class II induction in human islet cells by interferon-gamma plus tumour necrosis factor or lymphotoxin.

Abstract: HLA class II molecules are surface glycoproteins which are essential in the initiation of immune responses. It has been postulated that induction of class II in epithelial cells such as endocrine cells, which are normally class II negative, may result in autoimmunity. In type I diabetes, islet beta cells, the target of the autoimmune process, selectively express class II antigens. But in contrast to most other cell types, islet beta cells are not stimulated to express class II by interferon-gamma (IFN-gamma) and thus the conditions under which this induction occurs have been particularly elusive. The cytotoxins tumour necrosis factor (TNF) and lymphotoxin (LT) synergize with IFN-gamma in a number of activities. We report here that IFN-gamma in combination with either TNF or LT induces islet cell class II expression. This finding has important implications for the pathogenesis of type I diabetes and the understanding of the differential control of class II expression.

Cytotoxic T lymphocytes recognize a fragment of influenza virus matrix protein in association with HLA-A2.

Abstract: Both human and murine cytotoxic T cells (CTL) elicited in response to infection with influenza A viruses have been shown to be specific for internal viral proteins, such as the matrix and nucleoprotein1–3. Individual CTL epitopes have been identified in the nucleoprotein by successfully substituting short synthetic peptides for the intact virus in the preparation of target cells in cytotoxicity assays4. The defined peptide epitopes have each been recognized by CTL in association with individual class I major histocompatibility complex (MHC) proteins, H–2Db (ref. 4), H–2Kk (ref. 5), H–2Kd (Taylor, P. et al., unpublished data) and HLA-B37 (refs 4,6). A logical strategy to investigate the molecular details of the interaction between antigen and MHC class I proteins would be to define an epitope recognized by the MHC class I molecule HLA-A2. This is because the amino-acid sequence is known, several variants of A2 have been characterized and the protein has been purified and crystallized7–11. Here we describe a peptide derived from the influenza matrix protein that is recognized by human CTL in association with the HLA-A2 molecule.

Molecular genetic evidence for heterogeneity in manic depression.

Abstract: Manic depression is a severe cyclic mental illness that can be unipolar or bipolar and has a lifetime risk of approximately 7 per 1,000 in most populations. Families with multiple cases of manic depression have been described that are compatible with both autosomal dominant and X-linked modes of genetic transmission. Psychoactive antidepressant and stimulant drugs that help to ameliorate depression and mania are thought to act by affecting catecholamine neurotransmitter systems such as adrenaline, noradrenaline and dopamine, amongst others. Mutations affecting the tyrosine hydroxylase (TH) gene, which encodes the rate-limiting enzyme for the synthesis of these three neurotransmitters, might therefore be responsible for causing the manic depressive phenotype. We have studied three Icelandic kindreds amongst whom it appears that a single autosomal dominant disease allele is segregating. In these families there were 44 cases amongst 73 individuals at risk. Genetic linkage studies were carried out using clones encoding tyrosine hydroxylase the variable portion of the Harvey-ras-1 (HRAS1) locus and the variable region of the insulin gene (INS). All three markers are closely linked on chromosome 11 and were used to observe the segregation of restriction fragment length polymorphisms (RFLPs) in the three affected kindreds. We found no evidence for linkage to these markers in any of the three families. In contrast, Gerhard et al. found linkage between manic depression and HRAS1 in a single large Amish kindred. We conclude that there is genetic heterogeneity of linkage in manic depression. Therefore mutations at different loci are responsible for the manic depressive phenotype in the Amish and in Iceland.

An ultrastructural study of the early development and tissue cyst formation of Toxoplasma gondii in the brains of mice.

Abstract: The ultrastructural features of the early development and tissue cyst formation of Toxoplasma gondii were examined in the brains of mice at various intervals from 7 days to 22 months post inoculation (PI). At 11 days PI toxoplasms, with the ultrastructural features of the proliferative (endozoite) form, were identified undergoing multiplication within both inflammatory and neural cells. Early tissue cyst formation was also observed, predominantly within neurons. By 21 days PI the proliferative forms had disappeared and only developing tissue cysts containing densely packed cystozoites were present. The proportion of dividing cystozoites decreased with increasing size and age of the cysts. The wall of the tissue cyst developed as an adaptation of the lining of the parasitophorous vacuole. In the majority of older cysts, numerous tubular structures were present beneath the cyst wall. All the cysts observed were retained within intact host cells. The only morphological change with increasing age was that a proportion of the older cysts contained loosely packed cystozoites in an electron lucent ground substance. There was no evidence of any degenerative changes within the cystozoites.

Preferential deletion of exons in Duchenne and Becker muscular dystrophies

Abstract: Duchenne and Becker muscular dystrophy (DMD and BMD) genes are located in Xp21 on the short arm of the X chromosome. DMD patients display a much more severe clinical course than BMD patients, and yet about 10% of cases of each have been reported to have deletions for parts of the gene. Using a complementary DNA subclone of the DMD gene we have screened 66 DMD and BMD patients who had not previously shown deletions with the probes then available. Fifteen patients have a deletion of this part of the gene, indicating a higher deletion frequency in this region (22%). Exons were deleted in five severely affected DMD patients and in ten BMD patients. Significantly, most of these deletions begin in the same region of the cDNA, which implies that there is a common mechanism for the generation of many of these mutations. An apparently identical deletion in one family gave classical BMD in two brothers (presenting in their teens) and only very mild muscle weakness in their 86-year-old great-great-uncle. Taking these data together with data using the probes previously published, we are able to detect deletions directly in 40% of our families requiring antenatal diagnosis or carrier detection.

Cytokeratin expression in smooth muscle and smooth muscle tumours.

Abstract: The expression of cytokeratin intermediate filaments by a tumour has been accepted as evidence of an epithelial origin. Although there have been anecdotal reports of cytokeratin expression within tissues and neoplasms of non-epithelial origin, particularly muscle, there have been no comprehensive studies of its frequency and distribution. In order to investigate this we have studied 51 cases of normal smooth muscle and benign and malignant smooth muscle tumours using a panel of monoclonal antibodies against a range of intermediate filaments (cytokeratins, desmin and vimentin). Cytokeratin expression was noted overall in 50% of normal, benign and malignant smooth muscle tissues. Such expression tended to have a focal or patchy distribution. No case expressed cytokeratins in the absence of both desmin and vimentin. The implication of these findings for diagnostic immunocytochemistry is that intermediate filaments alone are not completely reliable markers of tumour histogenesis and should be used as part of a larger panel of monoclonal antibodies.

Detection of low copy human papilloma virus DNA and mRNA in routine paraffin sections of cervix by non-isotopic in situ hybridisation.

Abstract: In analysing human papilloma virus (HPV) infection of the cervix in formalin fixed paraffin sections by non-isotopic in situ hybridisation two main problems were found: detachment of sections from the glass during hybridisation and probe detection; inadequate sensitivity and inability to assess sensitivity of the in situ procedure. The first problem was investigated by assessing the efficiency of various tissue adhesives individually and in combination. The second problem was addressed by optimising conditions for DNA unmasking, hybridisation, and biotinylated probe detection. Sensitivity of the final in situ procedure developed was assessed by using the detection of pHY2.1 repeats as a built-in control. Extrapolation of data showed that less than 10 copies of HPV DNA can be visualised by these procedures. HPV nucleic acid, mainly in the form of DNA, was detected not only in koilocytic nuclei but also in suprabasal cells in condylomas and CIN lesions. HPV mRNA was also visualised in the cytoplasm (and probably also nuclei) of the same cell types. These non-isotopic in situ procedures give results comparable to those obtained with radiolabelled probes, but they are less time consuming and provide better morphological resolution.

An immunohistochemical study of differentiation in malignant fibrous histiocytoma.

Abstract: Immunohistochemistry was used to examine 10 cases of malignant fibrous histiocytoma. Malignant cells in all cases expressed vimentin and in eight there was co-expression of either desmin or neurofilament, both of these being present in four cases. In addition, cytokeratin was found in one case. In each tumour, a population of small cells was identified which had the staining characteristics of benign macrophages, and this was distinct from the tumour cells. This study supports the concept that malignant fibrous histiocytoma is a tumour of mesenchymal cells rather than of histiocytes and emphasizes the diversity of its cytostructure.

High peep decreases hyaline membrane formation in surfactant deficient lungs

Abstract: Lung lav age was performed in 16 anaesthetized rabbits to produce surfactant-deficient lungs. This resulted in alveolar collapse, an arterial Po2 of less than 15kPa on 100% oxygen and an inflection point on the inspirator/ limb of the pressure-volume curve at an airway pressure of 8–10 mm Hg. One group of eight animals was then ventilated with a positive end-expiratory pressure (PEEP) equal to the pressure at the inflection point, whilst the second group of eight was ventilated with a PEEP 5 mm Hg less than the inflection point. Animals in the high PEEP group had a significantly greater arterial P02 than those in the low PEEP group, but the mean survival time for each group was similar. However, there was a significantly greater incidence of hyaline membranes in the low PEEP group. Various mechanisms to explain these findings are discussed.

Association of thalassaemia intermedia with a beta-globin gene haplotype

Abstract: We have identified 14 Asian patients with homozygous beta zero thalassaemia who had a mild clinical disorder related to an augmented production of haemoglobin F. None of their parents had an elevated level of Hb F. Restriction fragment length polymorphism analysis of the beta-globin cluster of these patients and a control group of Asian thalassaemia major patients showed that 6/14 of the thalassaemia intermedia patients were homozygous for a particular 5' beta-globin haplotype (-+-++), in contrast to 1/42 of the thalassaemia major patients. Furthermore, the -+-++ beta haplotype is also associated with amelioration of disease severity in beta thalassaemia in an Italian population. This beta haplotype is linked to a DNA sequence variation 5' (at position -158) to the G gamma globin gene which can be detected by the presence (+) of an Xmn I restriction enzyme site. The possible role of the Xmn I-gamma polymorphism in relation to this variant HPFH is discussed. We conclude that much of the observed clinical variability of beta thalassaemia can now be explained by the inheritance of beta thalassaemia chromosomes with different propensities for fetal haemoglobin production.

Genotypic analysis of large cell lymphomas which express the Ki-1 antigen.

Abstract: The monoclonal antibody Ki-1 reacts with Reed-Sternberg cells in Hodgkin's disease and with the tumour cells in a minority of large cell non-Hodgkin's lymphomas. This study describes the results of immunophenotypic and DNA analysis in 30 cases of non-Hodgkin's lymphoma, all of which expressed the Ki-1 antigen. The genotypic analysis has been undertaken using both immunoglobulin and T-cell receptor gene probes. Sixteen cases were shown by this method to be of monoclonal T-cell origin, six of B-cell origin, while in eight cases there was no evidence of either T- or B-cell lineage. This confirms previous immunohistological data indicating that non-Hodgkin's lymphomas which express the Ki-1 antigen may be of either T-cell or B-cell origin.

The host-parasite relationship of Toxoplasma gondii in the brains of chronically infected mice.

Abstract: The host parasite relationship in the brains of asymptomatic mice chronically infected withToxoplasma gondii was examined at 3, 6 and 12 months post-infection (PI) using electron microscopy. The parasites were located in large numbers within tissue cysts which ranged in size from 10–50 µm in diameter. The cysts were predominantly found in the grey matter. The toxoplasms were enclosed by a cyst wall consisting of a membrane, with irregular invaginations, and an underlying layer of homogeneous osmiophilic material. A detailed examination of 50 cysts revealed that all the cysts were present within intact host cells irrespective of their size or the period PI. The majority of host cells could be positively identified as neurons by the presence of synapses. No extracellular cysts were observed. It is probable that the intracellular location of the cysts protects them from recognition and attack by the host immune system.

GT to AT transition at a splice donor site causes skipping of the preceding exon in phenylketonuria.

Abstract: Classical Phenylketonuria (PKU) is an autosomal recessive human genetic disorder caused by a deficiency of hepatic phenylalanine hydroxylase (PAH). We isolated several mutant PAH cDNA clones from a PKU carrier individual and showed that they contained an internal 116 base pair deletion, corresponding precisely to exon 12 of the human chromosomal PAH gene. The deletion causes the synthesis of a truncated protein lacking the C-terminal 52 amino acids. Gene transfer and expression studies using the mutant PAH cDNA indicated that the deletion abolishes PAH activity in the cell as a result of protein instability. To determine the molecular basis of the deletion, the mutant chromosomal PAH gene was isolated from this individual and shown to contain a GT-- greater than AT substitution at the 5' splice donor site of intron 12. Thus, the consequence of the splice donor site mutation in the human liver is the skipping of the preceding exon during RNA splicing.

Pathophysiology of severe falciparum malaria in man.

Abstract: The term severe falciparum malaria implies an infection with manifestations and complications which are potentially fatal in man, the natural host for this parasite. Much that has been written on the pathophysiology of animal malarias is of doubtful relevance to the understanding of the mechanism of Plasmodium falciparum infection in man. The clinical picture of severe P. falciparum infection differs in several respects from severe animal malarias, even those of non-human primates. Cerebral dysfunction is the most common severe manifestation of falciparum malaria in man. Coma develops suddenly after a generalized convulsion or gradually towards the end of the first week of illness. There are signs of a symmetrical upper motor neurone lesion and brain-stem dysfunction, but only about 5% of survivors show persisting neurological deficit after 2 or 3 days of unconsciousness. The mortality of cerebral malaria depends on how it is defined and on the predominant age group and other factors. In patients with proved acute P. falciparum infection with unrousable coma, in whom other causes of encephalopathy have been excluded, the mortality is between 15 and 50% despite treatment with antimalarial drugs (Warrell, Looareesuwan, Warrell, Kasemsarn, Intaraprasert, Bunnag & Harinasuta, 1982).

The effect of anti-L3T4 monoclonal antibody treatment on first-set rejection of murine cardiac allografts.

Abstract: Le traitement par anticorps de rat dirige contre les cellules de souris L3T4 prolonge la survie d'allogreffes de cœur chez la souris immunocompetente naive, probablement en provoquant une depletion de la sous population de cellules T L3T4 +

Common genetic disorders of the red cell and the 'malaria hypothesis'.

Abstract: Cette etude aborde successivement la distribution mondiale des polymorphismes cellulaires, les origines et mouvements des genes pour les polymorphismes erythrocytaires communs, la distribution mondiale des variantes erythrocytaires commune et leur association au paludisme actuel ou passe, les mecanismes cellulaires de la protection contre le paludisme a P. falciparum