Search PubMed⌕ Search

Biomedical subjects

A Todd

Publications and source records attributed to A Todd.

At least 37 records · Page 2Linked to original sources
PubMed1998

Human cruciform binding protein belongs to the 14-3-3 family.

Cruciform DNA has been implicated in the initiation of DNA replication. Recently, we identified and purified from human (HeLa) cells a protein, CBP, with binding specificity for cruciform DNA. We have reported previously that the CBP activity sediments at approximately 66 kDa in a glycerol gradient. Here, photochemical cross-linking studies and Southwestern analyses confirm that a 70 kDa polypeptide interacts specifically with cruciform DNA. Microsequence analysis of tryptic peptides of the 70 kDa CBP reveals that it is 100% homologous to the 14-3-3 family of proteins and shows that CBP contains the epsilon, beta, gamma, and zeta isoforms of the 14-3-3 family. In addition to polypeptides with the characteristic molecular mass of 14-3-3 proteins (30 and 33 kDa), CBP also contains a polypeptide of 35 kDa which is recognized by an antibody specific for the epsilon isoform of 14-3-3. Cruciform-specific binding activity is also detected in 14-3-3 proteins purified from sheep brain. Immunofluorescene studies confirm the presence of the epsilon, beta, and zeta isoforms of 14-3-3 proteins in the nuclei of HeLa cells. The 14-3-3 family of proteins has been implicated in cell cycle control, and members of this family have been shown to interact with various signaling proteins. Cruciform binding is a new activity associated with the 14-3-3 family.

14-3-3 Proteins↗
PubMed1998

Restriction endonuclease-mediated selective polymerase chain reaction: a novel assay for the detection of K-ras mutations in clinical samples.

The enriched polymerase chain reaction (PCR) assay has been used extensively in the detection of ras gene mutations in many types of human malignancies. Although it is very sensitive, it has a number of features that limit its use in the routine diagnostic laboratory. The aim of this study was to develop a novel enriched PCR strategy, in which the concurrent activity of the restriction enzyme BstNI and Taq polymerase allowed the amplification of mutant K-ras while inhibiting the formation of wild-type product. This restriction endonuclease-mediated selective PCR assay uses three sets of primers, together with BstNI, in the reaction mix, and the amplification products are analyzed by gel electrophoresis. The reliability of the restriction endonuclease-mediated selective PCR assay to detect activated K-ras was determined in a variety of clinical samples, including 139 fresh colorectal carcinomas and 113 paraffin-embedded blocks from 80 separate tumors of the colon and rectum, pancreas, breast, or kidney. Codon 12 mutations of the K-ras oncogene were identified in DNA from both fresh and paraffin-embedded tumors in a rapid, sensitive, and reproducible manner. Mutations were detected in 33 (24%) of the fresh colorectal cancers and 16 (20%) of the paraffin-embedded tumors. These results were 97% concordant in cases in which paraffin blocks and fresh specimens from the same tumor were available for analysis. We conclude that restriction endonuclease-mediated selective PCR is a sensitive, rapid, and robust assay for the detection of point mutations in a variety of clinical samples. Importantly, there is no need for manipulation of the sample once the PCR has been set up, and therefore, the chance of contamination is significantly reduced. In contrast to previous assays, restriction endonuclease-mediated selective PCR is not labor intensive, and its format is suitable for use in routine diagnostic laboratory.

Adenocarcinoma↗
PubMed1998

IgG subclass responses to pigeon intestinal mucin are related to development of pigeon fanciers' lung.

BACKGROUND: Pigeon fanciers' lung (PFL) is a form of extrinsic allergic alveolitis. Affected individuals produce antibodies to various pigeon antigens, and the resulting immune complexes are thought to initiate the disease. However, high antibody titres also occur in some asymptomatic individuals. Previously attention has focused on protein antigens, but we have recently identified pigeon intestinal mucin as a novel antigen in PFL. OBJECTIVE: To determine the relationship between IgG subclass antibodies to pigeon intestinal mucin and the development of pigeon fanciers' lung. METHODS: Sera were collected from 250 pigeon fanciers, who also completed a clinical questionnaire. Sera were screened for precipitating antibodies to pigeon serum and droppings. Individuals with symptoms and precipitating antibodies were considered to have classical PFL. Serum IgG and IgG subclass antibodies to pigeon intestinal mucin and pigeon serum proteins were investigated by quantitative enzyme-linked immunosorbent assay (ELISA). RESULTS: Very high titres of IgG antibodies against pigeon mucin were found in all precipitin-positive individuals. A strong positive correlation was seen between titres of antibodies to mucin and to serum proteins, but this was not due to crossreactivity. No significant differences in IgG titres to either mucin or pigeon serum proteins were found between individuals with PFL and asymptomatic precipitin positive fanciers. IgG1 and IgG2 were the major subclasses of anti-mucin, with lower titres of IgG3. Patients with PFL had significantly higher titres of IgG1 to mucin than asymptomatic, precipitin-positive individuals. In contrast, no significant differences were seen between PFL and asymptomatic precipitin-positive sera with respect to the subclass titres against pigeon serum proteins. CONCLUSION: The high titres of anti-mucin IgG in sera of all individuals with PFL, together with the finding that high IgG1 titres to mucin are associated with the development of disease confirm pigeon intestinal mucin as an important antigen in PFL.

Adult↗
PubMed1998

Pigeon fanciers' lung: effects of smoking on serum and salivary antibody responses to pigeon antigens.

A reduced prevalence of pigeon fanciers' lung has been reported in pigeon breeders who smoke cigarettes. Serum and salivary antibodies to pigeon intestinal mucin and pigeon serum proteins were investigated in 227 pigeon fanciers, subdivided according to smoking habit and clinical status. Smokers had a lower incidence of precipitating antibodies to pigeon antigens and lower titres of serum IgG and IgA antibodies to mucin and to pigeon serum proteins in ELISA compared with non-smokers and ex-smokers. In contrast, IgG antibody titres to tetanus toxoid were similar in smoking and non-smoking groups. In contrast to serum antibodies, salivary IgA antibody titres to pigeon antigens were similar in smokers and non- or ex-smokers. Approximately one third of the smokers reported symptoms consistent with pigeon fanciers' lung but did not have precipitating antibodies. Only some individuals with precipitating antibodies had disease symptoms, and IgG antibody titres in these individuals were not significantly higher than in many asymptomatic individuals. Salivary IgA titres against pigeon mucin were significantly higher in asymptomatic individuals, consistent with a protective role for these antibodies. The results confirm that smoking is associated with a decreased serum antibody response to inhaled pigeon antigens, affecting IgG1, IgG2 and IgA responses, but this impairment does not extend to salivary IgA or to antibody responses to a parenterally administered protein antigen. The fact that responses to pigeon serum proteins and to pigeon intestinal mucin were similarly affected suggests that cigarette smoking depresses both T-independent and T-dependent responses to inhaled antigens.

Animals↗
PubMed1998

Lead absorption and renal dysfunction in a South African battery factory.

OBJECTIVES: To test the association between inorganic lead (Pb) exposure, blood pressure, and renal function in South African battery factory workers, with both conventional and newer measures of renal function and integrity. METHODS: Renal function measures included serum creatinine, urea, and urate (n = 382). Urinary markers (n = 199) included urinary N-acetyl-beta-D-glucosaminidase (NAG), retinol binding protein, intestinal alkaline phosphatase, tissue non-specific alkaline phosphatase, Tamm-Horsfall glycoprotein, epidermal growth factor, and microalbuminuria. RESULTS: Mean current blood Pb was 53.5 micrograms/dl (range 23 to 110), median zinc protoporphyrin 10.9 micrograms/g haemoglobin (range 1.9 to 104), and mean exposure duration 11.6 years (range 0.5 to 44.5). Mean historical blood Pb, available on 246 workers, was 57.3 micrograms/dl (range 14 to 96.3). After adjustment for age, weight and height, positive exposure response relations were found between current blood Pb, historical blood Pb, zinc protoporphyrin (ZPP), and serum creatinine and urate. Blood pressure was not associated with Pb exposure. Among the urinary markers, only NAG showed a positive association with current and historical blood Pb. CONCLUSION: An exposure-response relation between Pb and renal dysfunction across the range from < 40 to > 70 micrograms/dl blood Pb was found in this workforce, with conventional measures of short and long term Pb exposure and of renal function. This could not be explained by an effect on blood pressure, which was not associated with Pb exposure. The findings probably reflect a higher cumulative renal burden of Pb absorption in this workforce in comparison with those in recent negative studies. The results also confirm the need for strategies to reduce Pb exposure among industrial workers in South Africa.

Acetylglucosaminidase↗
PubMed1998

Pigeon fanciers' lung: the mucin antigen is present in pigeon droppings and pigeon bloom.

BACKGROUND: Pigeon intestinal mucin has been implicated as an important antigen pigeon fanciers' lung. This study investigated whether mucin is detectable in pigeon droppings and bloom, the likely antigenic sources in disease. METHODS: Soluble extracts of a number of materials found in a pigeon loft were prepared and specific IgG subclass antibodies to these antigens were measured in 14 antibody-positive pigeon fanciers. Cross-reactivity between these materials and purified pigeon intestinal mucin was investigated by inhibition of anti-mucin ELISA. Mucin was purified from the soluble extracts of these crude antigen mixtures by CsCl density gradient centrifugation. RESULTS: The patterns of IgG subclass responses to purified pigeon intestinal mucin and to the four materials collected from the pigeon loft were similar. Subclass differences between symptomatic and asymptomatic individuals, demonstrable against purified mucin, were similarly seen against pigeon droppings and pigeon bloom. Both pigeon droppings and pigeon bloom were capable of inhibiting IgG binding to purified pigeon mucin, and mucin inhibited substantially the binding of IgG to these materials. Glycoprotein with a density similar to that described for pigeon intestinal mucin was purified from each source. CONCLUSION: Pigeon intestinal mucin is present in a variety of materials found in the environment of the pigeon loft in a form capable of reacting with anti-mucin antibodies in the sera of exposed individuals. Reduction in exposure to these materials may decrease the likelihood of developing pigeon fanciers' lung and minimise reactions in sensitised individuals.

Animals↗
PubMed1997

Photochemical formation of singlet molecular oxygen ((1)O2) in illuminated 6-methylcoumarin solutions.

Use of the fragrance 6-methylcoumarin (6-MC) in cosmetic products has declined significantly due to numerous reports of photoallergic contact dermatitis associated with its use. We have determined that 6-MC undergoes direct photolysis with an estimated half-life of 83 minutes when illuminated with mid-latitude U.S., noon-centered, equinox sunlight and a quantum yield for photolysis at 313 nm of phi = 3 x 10(-3). The work presented here also provides evidence that singlet molecular oxygen ((1)O2) is formed in illuminated solutions containing 6-MC. An estimated value of phi = 0.01 is reported for the (1)O2 quantum yield at 313 nm. Formation of (1)O2 is significant because it is known to react with a variety of biomolecules and it is possible that (1)O2 formation is at least partially responsible for reports of 6-MC photoallergenicity and phototoxicity.

Coumarins↗
PubMed1997

Monozygotic twins with Crohn's disease and ulcerative colitis: a unique case report.

BACKGROUND: A large number of monozygotic and dizygotic twin pairs with inflammatory bowel disease have been reported. To date no twin pair has developed phenotypically discordant inflammatory bowel disease. This case report is the first documented occurrence of discordant inflammatory bowel disease occurring in monozygotic twins. CASE REPORT: Twenty two year old identical male twins presented within three months of each other with inflammatory bowel disease that proved to be discordant in overall disease type, disease distribution, clinical course, and histopathological findings. Twin 1 developed a severe pancolitis necessitating total colectomy while twin 2 developed a predominantly distal patchy colitis with frequent granulomas, controlled by aminosalicylates. Twin 1 was antineutrophil cytoplasmic antibody (ANCA) negative at the time of testing while twin 2 (Crohn's disease) was ANCA positive. Significantly, the twins possessed the HLA type DR3-DR52-DQ2 previously associated with extensive colitis. CONCLUSION: This case report confirms the important role played by genetic factors in the development of inflammatory bowel disease. It also highlights the crucial role of undetermined environmental agents in dictating disease expression and phenotype.

Adult↗
PubMed1997

Neurogenic chronic idiopathic intestinal pseudo-obstruction, patent ductus arteriosus, and thrombocytopenia segregating as an X linked recessive disorder.

We present a family with three affected males in two generations with congenital neurogenic chronic idiopathic intestinal pseudo-obstruction (CIIP), patent ductus arteriosus, and large platelet thrombocytopenia apparently segregating as an X linked recessive disorder. The pattern of segregation of DNA markers within the family is consistent with linkage to the previously described neurogenic CIIP (CIIPX) locus at Xq28. This combination may represent a new contiguous gene disorder and appears to have a good prognosis with supportive therapy.

Abnormalities, Multiple↗
PubMed1996

Growth status of homeless Nepali boys: do they differ from rural and urban controls?

The rapid increase in numbers of homeless children in cities of the developed and developing world is a matter of grave concern. A multi-disciplinary study was undertaken to examine the health and lifestyles of the homeless in Nepal in comparison to other local children. Few studies have quantified the health of street-children in the developing world using anthropometric indicators, and to our knowledge this is the first to systematically compare the homeless with appropriate controls from both rural and urban areas. Heights and weights were measured for 307 six to fourteen year-old boys (III homeless 62 squatter, 82 privileged school and 52 village boys). Height for age (HAz), weight for age (WAz) and weight for height (WHz) I-scores relative to reference data from the National Center for Health Statistics (NCHS) were used as indicators of growth status. Stunting characterized all but the school-boys, but wasting was not observed. the homeless were less stunted than either poor squatter or village boys. On arrival on the streets, they were taller than village boys, and duration of homelessness had no effect on their growth status. Thus in terms of physical growth, and despite frequent health complaints, homeless boys in Nepal fare relatively better than control groups of poor urban and rural boys. Comparative studies which reveal some successful aspects of street-life show that urban homelessness may represent an appropriate response to circumstances of poverty.

Adolescent↗
PubMed1996

Bacterial meningitis--the importance of cerebro-spinal fluid examination.

The role of lumbar puncture in bacterial meningitis has been debated in recent years, especially in the presence of worsening headache, alteration of conscious level, focal neurological signs, papilloedema or a haemorrhagic rash. However valuable bacteriological and epidemiological information will be lost if lumbar puncture is avoided, despite blood cultures being taken. This loss of information will be highlighted if pre-admission antibiotics are administered (this should now be standard practice).

Adolescent↗
PubMed1995

Deletion analysis of minimal sequence requirements for autonomous replication of ors8, a monkey early-replicating DNA sequence.

We have generated a panel of deletion mutants of ors8 (483 bp), a mammalian autonomously replicating DNA sequence, previously isolated by extrusion of nascent monkey (CV-1) DNA from replication bubbles active at the onset of S phase. The deletion mutants were tested for replication function by the DpnI resistance assay, in vivo, after transfection into HeLa cells, and in vitro. An internal fragment of 186-bp that is required for autonomous replication function of ors8 was identified. This fragment, when subcloned into pBR322 and similarly tested, was capable of autonomous replication in vivo and in vitro. The 186-bp fragment contains several repeated sequence motifs, such as the ATTA and ATTTAT motifs, occurring three and five times, respectively, the sequences TAGG and TAGA, occurring three and seven times, respectively, two 5'-ATT-3' repeats, a 44-bp imperfect inverted repeat (IR) sequence, and an imperfect consensus binding element for the transcription factor Oct-1. A measurable sequence-directed DNA curvature was also detected, coinciding with the AT-rich regions of the 186-bp fragment.

Animals↗
PubMed1994

Autonomous replication in vivo and in vitro of clones spanning the region of the DHFR origin of bidirectional replication (ori beta).

Plasmids containing the origin of bidirectional replication (ori beta) of the Chinese hamster dihydrofolate reductase-encoding gene (DHFR) were tested for autonomous replication in vivo and in vitro. The results show that plasmids pX24 and pneoS13, that contain a 4.8- and a 11.5-kb fragment, respectively, spanning the ori beta region, are able to replicate autonomously in human cells and in a cell-free system that uses human cell extracts. Another plasmid, pX14, containing a 4.8-kb fragment that is immediately adjacent to the ori beta region, also replicated in these two assays.

Animals↗
PubMed1993

The pharmacology of LY290324 in the guinea-pig: an orally active, potent and selective cysteinyl leukotriene receptor antagonist.

This study describes the evaluation of LY290324 as a leukotriene D4 (LTD4) receptor antagonist in guinea-pigs. In vitro, LY290324 was a potent and persistent antagonist of the contractile responses to LTD4 and LTE4 with pA2 values of 9.1 +/- 0.2 and 8.9 +/- 0.17 respectively. The antagonism appeared competitive and selective for LTD4/E4, as LY290324 (10(-6) M) had no effects on contraction elicited by LTC4, prostaglandin F2 alpha (PGF2 alpha), histamine and acetylcholine. In vivo the compound was highly effective in a dose-dependent manner by the intravenous, oral and inhaled routes in preventing LTD4-induced bronchospasm. Administered i.v. LY290324 prevented the development (ED50 = 3.4 micrograms/kg) of an LTD4-induced bronchospasm and readily reversed an established bronchospasm, but failed to prevent the bronchospasm to either histamine or platelet activating factor (PAF). Oral studies demonstrated efficacy for at least 12 h. Administered orally 6 h previously, LY290324 reduced LTC4, LTD4 and LTE4-induced bronchospasm with ED50s of 0.3, 0.28 and 0.37 mg/kg respectively. Relatively low inhaled levels (2 micrograms/kg) also significantly reduced (72.5%, P < 0.001) LTD4-induced bronchospasm. Finally the compound administered orally was effective in reducing antigen-induced bronchospasm in immunologically sensitised animals.

Administration, Inhalation↗