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J Charlton

Publications and source records attributed to J Charlton.

At least 55 records · Page 3Linked to original sources
PubMed1994

Sp1 sites in the mouse aprt gene promoter are required to prevent methylation of the CpG island.

In an attempt to find the mechanism by which CpG islands remain free of methylation we have undertaken a detailed examination of the mouse adenine phosphoribosyltransferase (aprt) gene. This housekeeping gene has a CpG island that extends over the gene promoter and includes the first two exons. We show that the island is free of methylation at all CpGs, whereas the flanks are methyated. Detailed patterns of methylation beyond the boundaries of the CpG island vary between cells. In vivo footprinting across the island region shows that three GC boxes clustered at the 5' edge of the CpG island are occupied, most probably by Sp1. No other footprints are detected within the island region. Deletion or mutagenesis of the Sp1 sites causes de novo methylation of the CpG island in a transgenic mouse assay. Thus, the peripherally located Sp1 sites are necessary to keep the aprt island methylation free.

Adenine Phosphoribosyltransferase↗
PubMed1994

The cold-sensitive period for frizzled in the development of wing hair polarity ends prior to the start of hair morphogenesis.

The function of the frizzled (fz) gene is essential for the development of the normal pattern of hairs on the Drosophila wing. In the absence of fz function hairs develop, but they display an abnormal polarity. Mutations in fz result in an altered subcellular location for the assembly of the F-actin filled prehair that becomes the adult cuticular hair. This observation led to the suggestion that fz and other tissue polarity genes form a regulatory pathway that controls the initiation of prehairs. We have isolated a cold-sensitive fz allele and found that the cold-sensitive period for fz in the pupal wing starts in the early pupae and ends prior to the first sign of prehair morphogenesis. This cold-sensitive mutation is due to a missense mutation in a putative transmembrane domain. Western blot analysis shows that the accumulation of the mutant protein is not cold sensitive, consistent with the supposition that it is the activity of the mutant protein that is cold sensitive. Our data argue that fz has a regulatory function in specifying where the prehair forms, but no role in the actual morphogenesis of the prehair.

Actins↗
PubMed1994

The Drosophila tissue polarity gene inturned functions prior to wing hair morphogenesis in the regulation of hair polarity and number.

The adult cuticular wing of Drosophila is covered with an array of distally pointing hairs. Mutations in the inturned (in) gene result in both abnormal hair polarity (i.e., hairs no longer point distally), and, in most cells forming more than one hair. We have isolated and characterized a collection of in alleles. Among this collection of alleles are a number of rearrangements that enable us to assign in to 77B3-5. Almost all of the in alleles, including putative null alleles, result in a stronger phenotype on the wing at 18 degrees than 29 degrees. The data argue that the in-dependent process is cold-sensitive. Temperature shift experiments with a hypomorphic allele show that this cold sensitivity can be relieved by several hours of incubation at the permissive temperature at a variety of times in the early pupae, but that this ability ends prior to the start of hair morphogenesis. One new allele showed a dramatic heat sensitivity. Temperature shift experiments with this allele revealed a very short temperature-sensitive period that is a few hours prior to the start of hair morphogenesis. That the temperature during hair morphogenesis is irrelevant for the phenotype of in is consistent with the hypothesis that the only role that in has in wing hair development is to regulate the initiation of hair morphogenesis.

Animals↗
PubMed1993

Prevalence of dental enamel defects in 6, 7 and 8-year-old children resident in West Bromwich, Sandwell, UK.

Prompted by a parent's concern about the enamel defects of his daughter's teeth, the present study surveyed a sample of 6-8-year-old children using a modified developmental defects of enamel index. The aim was to establish the prevalence of such defects in permanent teeth of children in West Bromwich and to investigate differences according to social class or ethnic origin. Results showed that the mouth and tooth prevalence of enamel defects in Sandwell were not higher than those reported in similar studies. Analysis revealed no statistical significance between the tooth or mouth prevalence of defects according to the social class of the child although significant differences were found between children of Asian and non-Asian origin. A greater prevalence of diffuse defects was found among non-Asian children, conversely there was a greater prevalence of demarcated defects among Asian children. Recommendations are made in relation to the conduct of future studies of a similar kind with regard to the number of teeth examined, the presentation of reproducibility results and the evaluation of the cosmetic appearance of the teeth.

Asia↗
PubMed1991

Phenotypic consequences and genetic interactions of a null mutation in the Drosophila Posterior Sex Combs gene.

The Posterior Sex Combs (Psc) gene of Drosophila is a member of the Polycomb (Pc) group of transregulatory genes. Previous analyses of the function of this gene in Drosophila embryogenesis have been hampered by the lack of a null mutation. We recently isolated a mutation that deletes the 5' end of the Psc gene. This allele appears to be a null mutation, and we have used it to determine the Psc zygotic null phenotype and to look at the interactions of a null allele of Psc with five other Pc group mutations. We find evidence for transformations along both the anterior-posterior and dorsal-ventral axes in embryos of a variety of genotypes that include a null mutation in Psc. The phenotypes of embryos that are doubly mutant for a null allele of Psc and a mutation in a second Pc group gene show dramatic synergistic effects, but in their specifics they are dependent on the identity of the second Pc group gene. This is different from the relatively uniform phenotypes seen among double mutants that contained the allele Psc1, which has both gain and loss of function properties. The differences in the phenotypes of the doubly mutant embryos allow us to eliminate one class of molecular models to explain the dramatic synergism seen with mutations in this group of genes.

Animals↗
PubMed1991

CAIII a marker for early myogenesis: analysis of expression in cultured myogenic cells.

Carbonic anhydrase III (CAIII) is an abundant muscle protein characteristic of adult type-1, slow-twitch, muscle fibers. We demonstrate that CAIII is not confined to mature muscle but is also expressed in cultured myogenic cells that were originally derived from adult and fetal limb muscle (G8 and C2C12) and by azacytidine treatment of 10T1/2 fibroblasts (23A2). Transcripts may accumulate in these cells to levels that correspond to 6.5% of that found in mature muscle. CAIII is expressed in mononucleate myoblasts and is abundant in those that preferentially fuse to form myotubes, and these findings contrast with those for many other muscle genes whose transcripts only accumulate on or after terminal differentiation. Preliminary promoter-function assays by transfection shows that 2.8 kb of sequence flanking the 5' end of the human CAIII gene efficiently promotes transcription of the bacterial chloramphenicol acetyltransferase gene in myogenic cells. However, none of the sequences within this region are sufficient to confer muscle-specific expression. Removal of sequences 5' to -715 bp leads to a major loss of transcriptional activity of the CAIII promoter. These results imply that the proximal CAIII promoter, which includes a putative CArG box and four potential MyoD binding sites, is not adequate for either myoblast-specific or maximal transcription.

Animals↗
PubMed1989

Myosin regulation and calcium transients in fibroblast shape change, attachment, and patching.

Following our study in Balb/c 3T3 cells and other cultured fibroblasts of the changes in myosin light chain phosphorylation associated with alterations in cell shape, attachment, and receptor patching, we have now determined the corresponding changes in cytoskeletal myosin distribution, and in the cellular calcium concentration, since this might, in part, mediate such responses. Immunofluorescence microscopy showed that myosin assembly into ordered forms such as actomyosin bundles and myosin sheath almost always correlated with previously shown high phosphorylation levels of myosin regulatory light chain, whereas diffuse distributions usually correlated with low or undetectable levels. An exception was observed in treatment to alter cellular cAMP levels when, in a biphasic response, assembly was correlated inversely with the phosphorylation states shown previously. Fluorescent indicators for intracellular calcium concentration, [Ca++]i, showed that myosin disassembly by trypsin or EGTA acting externally on the cells was preceded by a transient increase in [Ca++]i. For EGTA this was associated with transient recruitment of myosin into dorsal sheath structure as well as the transient enhancement of phosphorylation shown earlier. Blockage of EGTA-induced disassembly could be achieved by azide, which also caused an immediate increase in [Ca++]i and inhibited its subsequent decline. Trypsin-induced dephosphorylation did not appear to involve an eventual reduction of [Ca++]i. Therefore, in many but not all of the systems studied, correlated changes were observed in myosin assembly, [Ca++]i, and the myosin phosphorylation levels shown earlier.

Animals↗
PubMed1989

Genetic interactions of the suppressor 2 of zeste region genes.

A wide variety of gain of function mutations have been induced in the Posterior Sex Comb (Psc)--Aristapedioid (Arp)--Suppressor 2 of zeste (Su(z)2) region of the second chromosome of Drosophila. This region contains at least three apparently related genes, two of which we have been studying. Psc1 has previously been used to identify Psc as a Pc group gene; however, it is a complex mutation with both gain and loss of function character. We report here that the Pc group character of Psc is not due to a gain of function and presumably reflects the function of the wild-type gene. We also provide evidence for a maternal function for Psc, as well as the neighboring Su(z)2 gene. Su(z)2 does not appear to be a Pc group gene as it does not act in a synergistic fashion with other Pc group genes in promoting posteriorly directed transformations. However, we have found that mutations in Su(z)2 do interact in a variety of interesting ways with mutations in Pc group genes.

Alleles↗
PubMed1989

Effect of meptazinol on evoked responses in rat vas deferens.

Responses of rat isolated vas deferens to electrical stimulation through field electrodes (400 mA, 1 ms duration, single shocks at 5 min intervals) were potentiated by meptazinol (10 to 300 microM) in whole tissues and also in the separated prostatic and epididymal portions. The effect was fast in onset, reproducible and easily reversed by washing. Prazosin (0.1 microM) practically abolished the response of the epididymal portion to electrical stimulation while the response of the prostatic portion was only slightly reduced (less than 20%). In the presence of prazosin, meptazinol still produced potentiation of the response of the prostatic portion. Nifedipine (2 microM) practically abolished the response of the prostatic portion to electrical stimulation while the response of the epididymal portion was only slightly reduced (less than 20%). In the presence of nifedipine, meptazinol no longer produced potentiation of the response of the epididymal portion. Exogenous ATP (5 microM to 1 mM) and phenylephrine (1 to 50 microM) produced a contractile response which was potentiated in the presence of meptazinol (100 microM) but in the presence of meptazinol (100 microM) and nifedipine (5 mM) together, potentiation of phenylephrine no longer occurred. It is suggested that potentiation by meptazinol of electrically induced responses in this tissue is due to a direct action on the smooth muscle.

Animals↗
PubMed1989

Vasopressin secretion in the DIDMOAD (Wolfram) syndrome.

The diabetes insipidus which accompanies the DIDMOAD (Wolfram) syndrome is thought to be hypothalamic in origin, though no formal study of vasopressin secretion in the syndrome has been published, and some data in the literature suggest a renal tubular defect. We have studied vasopressin secretion in seven patients with the Wolfram/DIDMOAD syndrome during three dynamic stimuli: an osmotic stimulus (hypertonic saline infusion), hypoglycaemia (insulin tolerance test) and a baroregulatory stimulus (trimetaphan infusion). Hypertonic saline infusion demonstrated three patients to have complete and four to have partial hypothalamic diabetes insipidus; administration of (per nasal) desmopressin excluded nephrogenic diabetes insipidus in all seven patients. Insulin hypoglycaemia failed to stimulate vasopressin release, but trimetaphan-induced hypotension produced significant though subnormal rises in plasma vasopressin in three patients with partial diabetes insipidus, though it produced a negligible rise and no rise in plasma vasopressin in two patients with complete diabetes insipidus. The data suggest a much greater frequency of hypothalamic diabetes insipidus in the Wolfram/DIDMOAD syndrome than is reported, but did not identify nephrogenic diabetes insipidus. The absence of vasopressin responses to non-osmotic stimuli in patients with complete diabetes insipidus suggests global lack of vasopressin secreting neurones, rather than an isolated osmoreceptor defect or selective vasopressin secreting neuronal loss, as the lesion producing diabetes insipidus in the DIDMOAD syndrome.

Adult↗
PubMed1988

A non-methylated CpG-rich island associated with the human muscle-specific carbonic anhydrase III gene.

A cluster of CpG dinucleotides immediately upstream from exon 1 in the muscle-specific carbonic anhydrase III gene (CAIII) resembles the 'HpaII tiny fragment' (HTF) islands characteristic of mammalian 'housekeeping' genes. Since this CAIII gene shows tissue-specific expression we have carried out a detailed examination of methylation status within the CpG cluster using a polyacrylamide gel/electroblot procedure to extend the range of conventional Southern blotting. None of the clustered CpGs are methylated in DNA from muscle or other somatic tissues or in DNA from spermatozoa although flanking CpGs are methylated. Comparison with a candidate HTF island from the more ubiquitously expressed carbonic anhydrase II gene (CAII) shows that the CAII CpG cluster is markedly more CpG-rich than that from the strictly tissue-specific CAIII gene.

Carbonic Anhydrases↗
PubMed1987

Making access to health care more equal: the role of general medical services.

The Resource Allocation Working Party (RAWP) recognised the need to consider both health authority and primary care services in achieving its objective. RAWP and the subsequent Advisory Group on Resource Allocation (AGRA) found (but did not publish) considerable variation in resources used by both services but could not find a clear relation between them. Statistics provided by the DHSS were used to compare spending by 80 area health authorities in 1980-1 with expenditure per head on general medical services by their corresponding family practitioner committees. There was considerable variation in the provision of resources for both services and no clear relation between the variations in spending on each service. Only 40 of the 80 areas had both health authority and family practitioner committee spending levels within 10% of "target." Subregional inequalities in resources tend to be related to variations in admission rates, which in turn are related to general practitioners' referral behaviour. These results emphasise the importance of finding out more about inequalities in the provision of general medical services and their relation to the use of hospital services. They also suggest that RAWP's aim of equality of opportunity of access to health care resources may be achieved only if general medical services are brought into the equation as well.

Family Practice↗
PubMed1987

Induction of in vivo helper activity for murine antibody responses by macrophages pulsed with ovalbumin-monomethoxypolyethylene glycol (OA-mPEG) conjugates.

Conjugates of protein antigens with an optimal number of monomethoxypolyethylene glycol (mPEG) chains of an appropriate molecular weight had been shown to suppress murine IgE responses to the unmodified antigen. To investigate the possibility that the tolerogenic capacity of these mPEG conjugates is attributable to a defect in macrophage (M phi) presentation of their antigenic determinants, the activity of ovalbumin (OA)-mPEG conjugates when pulsed onto mouse peritoneal adherent cells (M phi) was compared in this study with their activity in solution. Surprisingly, in contrast to the suppressogenic capacity of mPEG conjugates in solution, the OA-mPEG pulsed M phi appeared to exert a helper effect when injected intraperitoneally (ip), i.e., after subsequent immunization with dinitrophenylated OA (DNP3-OA) in Al(OH)3, the mice showed accelerated IgE and IgG1 antibody responses to OA and DNP. However, when M phi were exposed to limiting concentrations of OA or OA-mPEG, markedly higher concentrations of OA-mPEG were required to yield pulsed M phi, exerting a significant helper effect. It was concluded that although M phi were capable of presenting the OA determinants of OA-mPEG conjugates to helper T (Th) cells, the preparations of modified antigen were presented less effectively than native OA.

Animals↗
PubMed1987

Human muscle carbonic anhydrase: gene structure and DNA methylation patterns in fetal and adult tissues.

We report the isolation and analysis of genomic clones comprising the entire gene coding for the human muscle carbonic anhydrase, CAIII. The gene spans 10.3 kb and has a seven-exon/six-intron structure. A noncanonical TATA box, a CCAAT motif, and two CCGCCC elements are present in the sequences upstream of exon 1. Although the expression of CAIII shows strict tissue specificity, the gene exhibits a number of features normally associated with housekeeping enzymes. For example, there is 48% homology with a 25-bp consensus sequence between the TATA box and the cap site and there is a CpG-rich island spanning a 469-bp sequence near to the origin of transcription. Methylation studies suggest that some CCGG sites clustered in the CpG-rich island are undermethylated in DNA from fetal and adult muscle and in other tissues irrespective of CAIII expression. In contrast, several nonclustered CCGG sites show a methylation pattern that correlates with gene expression. However DNA from differentiated type II adult muscle fibers is undermethylated at these sites even though CAIII is not expressed.

Adult↗
PubMed1987

Risk factors for mortality after bereavement: a logistic regression analysis.

A national sample of elderly widowed people was followed up for six years. Excess mortality was found for men aged 75 years and over in the first six months of bereavement compared with men of the same age in the general population. Logistic regression analysis, controlling for age and sex together, demonstrated that the best independent predictors of mortality among the elderly widowed were: interviewer assessment of low happiness level; interviewer assessed and self-reported problems with nerves and depression; and lack of telephone contacts. The general practitioner is well placed to assess levels of depression and unhappiness among the widowed and to check that they have adequate social support.

Aged↗