Biomedical subjects

C Dean

Publications and source records attributed to C Dean.

At least 109 records · Page 6Linked to original sources

PubMed1995

Patterns of gene action in plant development revealed by enhancer trap and gene trap transposable elements.

The crucifer Arabidopsis thaliana has been used widely as a model organism for the study of plant development. We describe here the development of an efficient insertional mutagenesis system in Arabidopsis that permits identification of genes by their patterns of expression during development. Transposable elements of the Ac/Ds system carrying the GUS reporter gene have been designed to act as enhancer traps or gene traps. A novel selection scheme maximizes recovery of unlinked transposition events. In this study 491 plants carrying independent transposon insertions were generated and screened for expression patterns. One-half of the enhancer trap insertions and one-quarter of the gene trap insertions displayed GUS expression in seedlings or flowers, including expression patterns specific to organs, tissues, cell types, or developmental stages. The patterns identify genes that act during organogenesis, pattern formation, or cell differentiation. Transposon insertion lines with specific GUS expression patterns provide valuable markers for studies of Arabidopsis development and identify new cell types or subtypes in plants. The diversity of gene expression patterns generated suggests that the identification and cloning of Arabidopsis genes expressed in any developmental process is feasible using this system.

Arabidopsis↗

PubMed1995

Discharge patterns of baroreceptor-modulated neurons in the nucleus tractus solitarius.

Activity of baroreceptor-modulated neurons in the nucleus tractus solitarius (NTS) was recorded extracellularly during selective pressure stimulation of carotid baroreceptors, using an isolated carotid sinus preparation in anesthetized dogs. One of two different patterns of activity was recorded from individual baro-sensitive neurons in response to slow ramp increases in carotid sinus pressure. The cause of these two distinct firing patterns is not known but preliminary results indicate that it may be due in part to input from different functional types of baroreceptors. These results suggest that some differentiation in blood pressure control may be encoded in the responses of central baro-sensitive neurons in the NTS.

Anesthesia↗

PubMed1995

An adoption study comparing the prevalence of psychiatric illness in women who have adoptive and natural children compared with women who have adoptive children only.

The current study compares the current and lifetime prevalence of affective disorder in women who have adopted and have natural children (n = 110) with women who only have adopted children (n = 176). There was no difference in lifetime prevalence of psychiatric disorder between the two groups and a nonsignificant trend for women who had born children to have had a major depressive episode during their lifetime 48 (44%) cf 62 (35%). The increased prevalence of psychiatric illness in married women with children cannot be explained by the biological fact of bearing children. None of the social variables related to child-rearing which were examined influenced the lifetime prevalence of psychiatric disorder.

Adoption↗

PubMed1995

The binding of HB-EGF to tumour cells is blocked by mAbs which act as EGF and TGF alpha antagonists.

Heparin binding EGF (HB-EGF), a newly discovered member of the EGF family of mitogens, binds to the EGF receptor (EGFR) and to heparan sulfate proteoglycans on the cell surface. Here, we show that the binding of HB-EGF to the EGFR is inhibited by mAbs which prevent the interaction of EGF and TGF alpha with the receptor. Also, we show that, like EGF and TGF alpha, treatment with HB-EGF inhibits the growth in vitro of tumours (HN5, HSC-4) that overexpress the EGFR. We conclude that mAbs which act as EGF and TGF alpha antagonists should also be effective therapeutic agents for blocking the growth of EGFR overexpressing tumours induced by HB-EGF.

Antibodies, Monoclonal↗

PubMed1995

Safety of intravenous valproate.

This multicenter, open-label trial was designed to study the safety of intravenous (IV) sodium valproate in patients with epilepsy. All 318 patients (previously treated with antiepileptic drugs) were hospitalized for seizure control or anticipated seizures. The protocol allowed physicians to set the number of infusions and treatment duration. Adverse events, laboratory studies performed, and seizure activity were documented on case report forms. The patients' mean age was 34.4 years (range, 2-87 years). The most common reason for admission was lack of seizure control (235 patients, 185 of whom were admitted for video-electroencephalographic monitoring). The median dosage of valproate was 375 mg infused over 1 hour. The median number of doses was four, given over 2 days. In 54 patients (17%), transient adverse events were reported. The most frequent were headache, reaction at the injection site, and nausea (2.2% each); somnolence (1.9%); vomiting (1.6%); and dizziness and taste perversion (1.3% each). No persistent or severe hematologic or serum chemistry abnormalities were found. Vital signs were not significantly affected by the IV infusion of valproate. At the dosages and rates of administration studied, intravenous valproate appears to be safe and well tolerated.

Adolescent↗

PubMed1995

TGF-betas upregulate NCAM and L1 expression in cultured Schwann cells, suppress cyclic AMP-induced expression of O4 and galactocerebroside, and are widely expressed in cells of the Schwann cell lineage in vivo.

We have examined both how the molecular phenotype of Schwann cells in vitro is regulated by transforming growth factor beta (TGF-beta), using immunohistochemistry and immunoblotting, and the distribution of TGF-beta 2 and 3 in embryonic and mature nerves and ganglia, using immunohistochemistry and in situ hybridisation. We find that TGF-beta 2 and -3 upregulate expression of the neural cell adhesion molecules NCAM and L1. In TGF-beta-treated cultures, in addition to the 140 and 120 kD isoforms known to be present in Schwann cells, small amounts of the 180 kD isoform can be detected. TGF-beta s also block cAMP-induced expression of the lipid antigens galactocerebroside (GalC) and O4, in addition to blocking expression of protein zero (P0), the major peripheral myelin glycoprotein, as previously shown. Using antibodies specific to TGF-beta 2 and -3, respectively, we confirm the presence of these proteins in myelin-forming Schwann cells and show also that TGF-beta 2 and -3 are clearly expressed by peripheral glia that are not involved in myelination. This includes Schwann cell precursors, embryonic Schwann cells, non-myelin-forming Schwann cells and satellite cells from adult nerves and ganglia, and neonatal Schwann cells in purified cultures without neurones. In situ hybridisation with a digoxygenin-labelled riboprobe reveals a strong TGF-beta 3 mRNA signal in Schwann cells, satellite cells, and some neurones. Schwann cells in culture also secrete TGF-beta in a latent form, whereas purified cultures of dorsal root ganglion neurones from 1-day-old rats secrete active TGF beta during the first 48 h in culture.

Animals↗

PubMed1995

Primary structure of the variable regions encoding antibody to NG2, a tumour-specific antigen on the rat chondrosarcoma HSN. Correlation of idiotypic specificities with amino acid sequences.

Eight syngeneic rat monoclonal antibodies that recognize structurally overlapping epitopes on the chondroitin proteoglycan NG2, a tumour-specific antigen on the chemically induced rat chondrosarcoma HSN, have been analysed for the sequence of their immunoglobulin heavy (H) and light (L) chain variable (V) regions. This analysis defined five groups of antibodies which are very similar for both the H and L chains and revealed that a wide range of different V regions are capable of binding to the same antigenic determinant. However, three mAbs, 11/160, ALN/12/17 and ALN/9/94, which recognize a sequential epitope, were found to use almost identical heavy (V-D-J) and light (V-J) chains in regions demonstrating an exclusivity in specific protein-protein interaction for this particular epitope. Two other mAbs, ALN/11/53 and AL/3/12, used similar V and J segments but totally different D regions. With the exception of the pair ALN/11/53 and AL/3/12, this grouping of antibodies matches that derived from the idiotypic specificity study we have reported previously. The reactivity pattern of Ab1 11/160, ALN/12/17 and ALN/9/94 with six anti-idiotopic mAbs raised against 11/160 demonstrated that the idiotope recognized by Ab2 HIM/3/41 was defined by a single amino acid, Asn, at position 52 within the CDR2 loop of the VH region; whereas the D region of Ab1 ALN/11/53 was implicated as the structural correlate of idiotypy. The substitution of AsnH52 influenced the Id recognition but Ag binding was not affected suggesting that Ab2 HIM/3/41 did not mimic the NG2 Ag.

Amino Acid Sequence↗

PubMed1995

Expression of c-fos protein in the nucleus tractus solitarius in response to physiological activation of carotid baroreceptors.

This study has utilized unilateral physiological pressure stimulation f a vascularly isolated carotid sinus combined with c-fos immunohistochemistry to locate neurons of the nucleus tractus solitarius which are activated by carotid baroreceptors in the anesthetized, vagotomized dog. Carotid baroreceptor stimulation primarily activated neurons in the ipsilateral commissural and medial subnuclei of the caudal nucleus tractus solitarius. In the intermediate and rostral nucleus tractus solitarius, carotid baroreceptor stimulation activated neurons in the dorsal and medial subnuclei. Results from this study also suggested that different subgroups of nucleus tractus solitarius neurons may be activated by baroreceptors with different pressure thresholds. The use of c-fos immunohistochemistry in this study has enabled the definition of populations of dorsal medullary neurons in the carotid baroreflex pathway. The results also suggest a different projection of carotid baroreceptors with different pressure thresholds.

Animals↗

PubMed1994

Modification of the 5' untranslated leader region of the maize Activator element leads to increased activity in Arabidopsis.

In contrast to its behavior in tobacco and tomato, the maize transposable element Ac is relatively inactive in Arabidopsis. We show here that removal of 537 bp within a CpG-rich region of the Ac 5' untranslated leader region significantly increases the excision frequency of the element in Arabidopsis. This increase did not appear to be correlated with the removal of sequences that are methylated in inactive Ac elements in maize, as these sites were not methylated in Ac elements in Arabidopsis transformants. The deletion within the 5' untranslated leader did not increase Ac activity by increasing levels of steady-state transposase mRNA, as assayed by RNase protection experiments. Moreover, there was no correlation between the levels of steady-state transposase mRNA and Ac element activity. This suggests that post-transcriptional regulation of Ac activity occurs in Arabidopsis.

Arabidopsis↗

PubMed1994

The chondroitin sulfate proteoglycan NG2 is a tumour-specific antigen on the chemically induced rat chondrosarcoma HSN.

N-terminal sequences of 19 and 11 amino acids obtained from 2 different tryptic fragments of the tumour-specific antigen on the chemically induced rat chondrosarcoma HSN show a 100% homology with the rat chondroitin sulfate proteoglycan NG2. Using a scheme of overlapping oligonucleotide primers we have cloned by PCR amplification the cDNA for the specific antigen of the HSN tumour that is immunogenic in immunocompetent CBH/Cbi rats and now report that its cDNA sequence is identical to that of NG2. The cDNA codes for a transmembrane protein of 2,325 amino acids with a large extracellular domain of 2,224 amino acids containing 2 cysteine-rich regions, a transmembrane domain (25 amino acids) and a short cytoplasmic tail (76 amino acids). The tumour-specific determinant was found to lie between amino acid residues 556 and 992 on the core glycoprotein.

Amino Acid Sequence↗

PubMed1994

Differentiation or immune destruction: two pathways for therapy of squamous cell carcinomas with antibodies to the epidermal growth factor receptor.

We have carried out an immunohistochemical investigation of xenografts of epidermal growth factor receptor (EGFR)-overexpressing tumors that have been induced to regress by treatment with rat monoclonal antibodies (mAbs) to the human EGFR [ICR16 (IgG2a), ICR62 (IgG2b), and ICR64 (IgG1)]. When mice bearing xenografts of the HN5 squamous cell carcinoma were treated for 5 days with mAb ICR62 or ICR16, the antibodies were found to be localized uniformly on the tumor cell membranes. However, the foci of tumor cells that remained following treatment with ICR62 were smaller than with ICR16 and the former showed a more pronounced host mononuclear cell infiltrate. Examination of the few tumors that had not regressed completely and were still present as static nodules 77 days following the final treatment with anti-EGFR mAbs revealed significant levels of therapeutic mAb in the nonviable areas of the tumors. The microscopic areas of apparently viable tumor cells that did not stain when only secondary antibody was used stained positive when the sections were treated first with an anti-EGFR antibody. This suggests that loss of the target antigen was not a significant factor and that these residual cells might be eradicated by further treatment with mAb. Furthermore, the finding of keratinized areas in the tumors undergoing regression suggested that the carcinoma cells had undergone terminal differentiation following exposure to antibody. This possibility was supported by the finding that treatment of HN5 cells in vitro with mAbs ICR16, ICR62, or ICR64 resulted in the accumulation of cells in the G0-G1 phases of the cell cycle and expression of the terminal differentiation markers involucrin and cytokeratin 10. We found no evidence of apoptosis in such cells. We conclude that antibodies which block the binding of EGF and transforming growth factor alpha to the EGFR can inhibit the growth of EGFR-overexpressing tumors by directing terminal differentiation and that a further therapeutic benefit may be obtained via immunological mechanisms with rat IgG2b mAbs such as ICR62.

Animals↗

PubMed1994

Immunotherapy with antibodies to the EGF receptor.

A series of rat monoclonal antibodies (MAbs) has been generated against the extracellular domain of the receptor for EGF which block the binding of EGF and TGF alpha to the receptor and inhibit the growth in vitro of a range of carcinoma cell lines that over-express the receptor for EGF. Some of these antibodies were able also to induce the complete regression of xenografts of EGFR-over-expressing tumours when treatment was started, either at the time of tumour inoculation or later when the tumours were established. The most effective of these antibodies was ICR62, which was also able to activate host immune effector functions. We conclude that antibodies which block growth-factor-ligand interaction can have a profound influence on the proliferative capacity of tumour cells in vivo and may have useful clinical application.

Animals↗

PubMed1994

Integration of CAPS markers into the RFLP map generated using recombinant inbred lines of Arabidopsis thaliana.

Konieczny and Ausubel have described a technique whereby Arabidopsis thaliana loci can be rapidly mapped to one of the ten chromosome arms using a small number of F2 progeny from crosses between the ecotypes Landsberg erecta and Columbia. The technique involves the use of 18 co-dominant, cleaved amplified polymorphic sequence (CAPS) markers which are evenly distributed throughout the Arabidopsis genome. We have mapped these 18 markers using recombinant inbred (RI) lines generated in our laboratory. These data enable a better integration of loci mapped relative to the CAPS markers into the restriction fragment length polymorphism (RFLP) map generated using Arabidopsis RI lines.

Arabidopsis↗

PubMed1994

Mapping FRI, a locus controlling flowering time and vernalization response in Arabidopsis thaliana.

Two loci FRI (FRIGIDA) and KRY (KRYOPHILA) have previously been identified as having major influences on the flowering time of the late-flowering, vernalization-responsive Arabidopsis ecotype, Stockholm. We report here on the mapping and subsequent analysis of these two loci. FRI was mapped to the top of chromosome 4 between markers w122 and m506, using restriction fragment length polymorphism (RFLP) analysis. Due to lack of segregation in of the late-flowering phenotype under the environmental conditions used, KRY could only be localized, by "subtractive genotyping", to chromosome 5 or part of chromosome 3. The map position of FRI indicates that it is not allelic to any of the late-flowering loci identified by mutagenesis of the early-flowering ecotype Landsberg erecta. The late-flowering phenotype conferred by the Stockholm allele of FRI is modified (towards earlier flowering) by Landsberg erecta alleles at an unknown number of loci, perhaps accounting for the absence of fri mutations among mutant lines recovered in Landsberg erecta.

Alleles↗

PubMed1994

Analysis of clones carrying repeated DNA sequences in two YAC libraries of Arabidopsis thaliana DNA.

YAC clones carrying repeated DNA sequences from the Arabidopsis thaliana genome have been characterized in two widely used Arabidopsis YAC libraries, the EG library and the EW library. Ribosomal, chloroplast and the paracentromeric repeat sequences are differentially represented in the two libraries. The coordinates of YAC clones hybridizing to these sequences are given. A high proportion of EG YAC clones were classified as containing chimaeric inserts because individual clones carried unique sequences and repetitive sequences originating from different locations in the genome. None of the EW YAC clones analysed were chimaeric in this way. YAC clones carrying tandemly repeated sequences, such as the paracentromeric or rDNA sequences, exhibited a high degree of instability. These observations need to be taken into account when using these libraries in the development of a physical map of the Arabidopsis genome and in chromosome walking experiments.

Arabidopsis↗

PubMed1994

Prevalence of postnatal psychiatric morbidity in mothers and fathers.

In the first study to systematically examine postnatal depression in fathers, we examined depression in 200 postnatal couples, using a two-stage design. The prevalence of depression ascertained by the 13-item Edinburgh Postnatal Depression Scale (EPDS), using a cut-off score for 'caseness' of 13 or more in an unselected postnatal sample, was 27.5% in mothers at six weeks postpartum, 25.7% in mothers at six months postpartum, 9.0% in fathers at six weeks postpartum, and 5.4% in fathers at six months postpartum. The prevalence did not differ significantly in either mothers or fathers from a control group of parents with children between three and five years of age. As expected, mothers had a significantly higher prevalence of psychiatric 'caseness' at both six weeks and six months postpartum than fathers. Fathers were significantly more likely to be cases if their partners were also cases. The hypothesis that different aetiological factors would be important in brief and persistent disorders in mothers was upheld.

Adult↗

PubMed1993

Comparison of community based service with hospital based service for people with acute, severe psychiatric illness.

OBJECTIVE: To compare the burden on relatives and outcome of people treated for severe acute psychiatric illness by a community service and a traditional hospital based service. DESIGN: Follow up of patients aged 16-65 who required admission to hospital or home treatment for psychiatric illness during January 1990 to February 1991. SETTING: Two Birmingham electoral wards, Sparkbrook and Small Heath; Sparkbrook has a community based service and Small Heath a traditional hospital based service. SUBJECTS: 69 patients from Sparkbrook and 55 from Small Health. MAIN OUTCOME MEASURES: Scores on present state examination, social behaviour assessment schedule, and general health questionnaire. RESULTS: 24 (35%) of Sparkbrook patients received some treatment in hospital during the initial episodes. Relatives of Sparkbrook patients were less distressed by their burden at the initial assessment than relatives of Small Health patients (mean score 0.11 v 0.29, p < 0.01). Relatives were also more satisfied with the support they received and the treatment received by patients. More patients from Sparkbrook than Small Health were in contact with a psychiatrist (81% (95% confidence interval 71% to 91%) v 62% (44% to 68%)) and community nurse (56% (44% to 68%) v 14% (13% to 24%)) one year after the initial episode. Sparkbrook patients spent significantly fewer days in hospital during the initial episode (8 days v 59 days) and the first year (20.6 v 67.9 days). CONCLUSION: The community based service is as effective as the hospital based service and is preferred by relatives. It is more effective in keeping people in long term contact with psychiatrists.

Acute Disease↗

PubMed1993

Identification of a mobile endogenous transposon in Arabidopsis thaliana.

A mobile endogenous transposable element, Tag1, has been identified in the plant Arabidopsis thaliana. Tag1 was found in the nitrate transporter gene, CHL1, of a chlorate-resistant mutant present in a population of plants containing an active maize Ac transposon. Tag1 excises from the chl1 gene producing chlorate-sensitive revertants with Tag1 or Tag1-related elements at different loci. Tag1 and related elements are present in the Landsberg but not Columbia or Wassilewskija ecotypes of Arabidopsis. Thus, Tag1 provides a tool for the insertional mutagenesis of plant genes essential for biological processes of agronomic importance.

Arabidopsis↗