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Biomedical subjects

A G Smith

Publications and source records attributed to A G Smith.

At least 145 records · Page 8Linked to original sources
PubMed1997

Basal cell carcinoma.

Basal cell carcinoma is the commonest malignancy in Caucasians with incidence rates of 300 per 100,000 reported in the USA. Rates are increasing at over 10% per year leading to a lifetime risk of 30%. Although mortality is low, the disease is responsible for considerable morbidity and places a substantial burden on health service provision in the UK. Furthermore, lesions may recur and patients often develop multiple tumours giving major implications for treatment and follow-up. Four main types of basal cell carcinoma are seen: nodulo-ulcerative; pigmented; morpheaform and superficial. Diagnosis is by histological evaluation although many tumours have a characteristic clinical appearance. The differential diagnosis is large. Identified risk factors include male gender, skin type 1, red/blonde hair and increasing age. Patients with basal cell carcinoma are more likely to develop malignant melanoma and squamous cell carcinoma but it is still unclear whether there is a link with internal malignancy. The main treatment modalities are surgery and radiotherapy. Each has advantages and disadvantages. The choice of treatment depends on many factors. Principles of treatment include identification of high-risk patients to enable early detection, complete removal of the lesion, and careful follow-up to detect recurrence or new lesions. Approximately 10% of tumours recur, depending on site, size and treatment modality. Metastatic basal cell carcinoma and the association of ultraviolet radiation to basal cell carcinoma risk are reviewed.

Basal Cell Carcinoma↗
PubMed1997

Risk factors for basal cell carcinoma in the UK: case-control study in 806 patients.

Basal cell carcinoma (BCC) is the commonest malignant neoplasm in white people. We present a large UK case-control study in which conditional logistic regression analysis of age-matched and gender-matched data sets was used to compare, first, cases with controls (n = 403) and second, patients having multiple BCC with those having a single BCC (n = 278). Eye/hair colour, occupation, skin type, social class, tumour site at presentation and smoking history were assessed. Social class 1/2, skin type 1, red/blonde hair and blue/green eyes were all related to BCC risk, social class most strongly (odds ratio 2.36, P = 0.007). Truncal site at presentation was a risk factor for the development of multiple BCC (odds ratio 4.03, P = 0.002). These data support the view that genetically mediated differences in ultraviolet responsiveness are important in BCC, though the scale of their effect is small. They may be exploitable in primary and secondary prevention as well as giving insights into pathogenesis. In particular, the fact that patients presenting with a truncal tumour are at increased risk of further BCC suggests that intermittent exposure in genetically predisposed individuals may contribute to a cancer susceptibility syndrome.

Basal Cell Carcinoma↗
PubMed1997

Local thrombolytic therapy in deep cerebral venous thrombosis.

Thrombosis of the deep cerebral venous system is a rare entity with a very poor prognosis. We report two patients with thrombosis of the internal cerebral veins and vein of Galen who responded to local urokinase. We review all 49 cases of deep cerebral venous thrombosis in the English literature. The mortality rate for patients treated with either IV heparin or local thrombolytics was 13% compared with 48% in untreated patients (p = 0.037). Based on this retrospective review of the literature and our two cases, we support the use of heparin or local thrombolytics in individual cases of deep cerebral venous thrombosis.

Adult↗
PubMed1997

Differentiation of embryonic stem cells into adipocytes in vitro.

Embryonic stem cells, derived from the inner cell mass of murine blastocysts, can be maintained in a totipotent state in vitro. In appropriate conditions embryonic stem cells have been shown to differentiate in vitro into various derivatives of all three primary germ layers. We describe in this paper conditions to induce differentiation of embryonic stem cells reliably and at high efficiency into adipocytes. A prerequisite is to treat early developing embryonic stem cell-derived embryoid bodies with retinoic acid for a precise period of time. Retinoic acid could not be substituted by adipogenic hormones nor by potent activators of peroxisome proliferator-activated receptors. Treatment with retinoic acid resulted in the subsequent appearance of large clusters of mature adipocytes in embryoid body outgrowths. Lipogenic and lipolytic activities as well as high level expression of adipocyte specific genes could be detected in these cultures. Analysis of expression of potential adipogenic genes, such as peroxisome proliferator-activated receptors gamma and delta and CCAAT/enhancer binding protein beta, during differentiation of retinoic acid-treated embryoid bodies has been performed. The temporal pattern of expression of genes encoding these nuclear factors resembled that found during mouse embryogenesis. The differentiation of embryonic stem cells into adipocytes will provide an invaluable model for the characterisation of the role of genes expressed during the adipocyte development programme and for the identification of new adipogenic regulatory genes.

Adipocytes↗
PubMed1996

Definition of HLA-DQ as a transplantation antigen.

Recent studies have demonstrated the importance of recipient HLA-DRB1 allele disparity in the development of acute graft-versus-host disease (GVHD) after unrelated donor marrow transplantation. The role of HLA-DQB1 allele disparity in this clinical setting is unknown. To elucidate the biological importance of HLA-DQB1, we conducted a retrospective analysis of 449 HLA-A, -B, and -DR serologically matched unrelated donor transplants. Molecular typing of HLA-DRB1 and HLA-DQB1 alleles revealed 335 DRB1 and DQB1 matched pairs; 41 DRB1 matched and DQB1 mismatched pairs; 48 DRB1 mismatched and DQB1 matched pairs; and 25 DRB1 and DQB1 mismatched pairs. The conditional probabilities of grades III-IV acute GVHD were 0.42, 0.61, 0.55, and 0.71, respectively. The relative risk of acute GVHD associated with a single locus HLA-DQB1 mismatch was 1.8 (1.1, 2.7; P = 0.01), and the risk associated with any HLA-DQB1 and/or HLA-DRB1 mismatch was 1.6 (1.2, 2.2; P = 0.003). These results provide evidence that HLA-DQ is a transplant antigen and suggest that evaluation of both HLA-DQB1 and HLA-DRB1 is necessary in selecting potential donors.

Adolescent↗
PubMed1996

A flower-specific gene encoding an osmotin-like protein from Lycopersicon esculentum.

The flower-specific cDNA Tomf216 representing an mRNA encoding an osmotin-like protein was identified by the differential screening of a cDNA library produced from mRNA extracted from premeiotic tomato flowers (Lycopersicon esculentum). The cDNA is 894 nucleotides in length and encodes a protein of 252 amino acids. The deduced protein has a molecular mass of 27.2 kDa, an N-terminal region predicted to be a signal sequence, and a predicted molecular mass of 24.7 kDa for the mature protein. The protein contains 16 cysteine residues and has 30% to 32% amino acid sequence identity to pathogenesis-related osmotins. The gene is expressed in flowers and fruit with the highest levels of transcript accumulation in pistils from flowers at anthesis. No expression was detected in vegetative organs.

Amino Acid Sequence↗
PubMed1996

Uroporphyria induced by 5-aminolaevulinic acid alone in Ahrd SWR mice.

In mice, depression of hepatic uroporphyrinogen decarboxylase (UROD) leading to porphyrin accumulation (uroporphyria) occurs with chlorinated ligands of the aryl hydrocarbon (AH) receptor especially after iron overload. However, in the absence of chlorinated ligands, iron itself will eventually cause uroporphyria, but this response is not associated with the Ahr genotype. These effects are potentiated by administration of the haem precursor 5-aminolaevulinate (ALA). The aim of this study was to investigate the effects of ALA alone. Prolonged administration of 2 mg ALA/mL in the drinking water to SWR mice also led to decarboxylase insufficiency (11% of control) and uroporphyria by 8 weeks, whereas DBA/2 mice did not show reduced enzyme activity. Both strains are considered AH nonresponsive and analysis of the Ahr gene using restriction fragment length polymorphism was consistent with SWR, like DBA/2, possessing the Ahrd allele. Exposure of isolated hepatocytes to ALA (150-500 microM) for up to 48 hr showed a significant accumulation of both uroporphyrin and coproporphyrin in the medium, which for uroporphyrin particularly was significantly greater with SWR than with DBA/2 cells. Basal in vivo CYP1A2 activity, measured as microsomal methoxyresorufin dealkylation, was significantly greater in SWR than in DBA/2 mice (1.3-fold), but it was unclear whether this was sufficient to explain the marked difference in sensitivities of the two strains. Despite SWR mice being AH nonresponsive, uroporphyria and decarboxylase depression after an initial iron overload and ALA for 3 weeks were greatly potentiated by a single dose (100 mg/kg) of hexachlorobenzene (a weak AH ligand). The results demonstrate that there is a genetic difference in mice independent of the Ahr genotype and response to iron, which influences the susceptibility to ALA-induced uroporphyria. Thus chemicals, iron and ALA can act independently, but also together, to cause porphyria in susceptible individuals.

Aminolevulinic Acid↗
PubMed1996

Multicentre prospective randomised trial of fludarabine versus cyclophosphamide, doxorubicin, and prednisone (CAP) for treatment of advanced-stage chronic lymphocytic leukaemia. The French Cooperative Group on CLL.

BACKGROUND: Fludarabine seems to be a promising treatment for patients with advanced chronic lymphocytic leukaemia (CLL). We compared fludarabine therapy with the combination of cyclophosphamide, doxorubicin, and prednisone (CAP) for treatment of CLL in a randomised, multicentre prospective trial. METHODS: Patients older than 18 years of age were entered into the study if they presented with previously untreated B-cell lineage CLL (B-CLL) of Binet stages B or C or relapsed B-CLL pretreated with chorambucil or similar non-anthracycline-containing regimens. Patients were randomly assigned to either fludarabine (25 mg/m2 per day on days 1-5) or CAP (cyclophosphamide 750 mg/m2 per day and doxorubicin 50 mg/m2 per day on day 1, and prednisone 40 mg/m2 per day on days 1-5), both given for six courses. FINDINGS: Of 196 evaluable patients, 100 were previously untreated whereas 96 patients had received prior therapy. Remission rates were significantly higher after fludarabine than CAP, with overall response rates of 60% and 44%, respectively (p = 0.023). A higher response rate to fludarabine was observed in both untreated (71% vs 60%, p = 0.26) and pretreated (48% vs 27%, p = 0.036) cases, although the difference was statistically significant only in pretreated cases. In the latter group, remission duration and survival did not differ between treatment groups with a median remission duration of 324 days after fludarabine and 179 days after CAP (p = 0.22) and median survival times of 728 days and 731 days, respectively. In untreated cases, on the other hand, fludarabine induced significantly longer remissions than CAP with the median not yet reached after fludarabine and a median of 208 days after CAP (p < 0.001). This effect also translated into a tendency towards longer overall survival after fludarabine (p = 0.087). Treatment-associated side-effects consisted in both regimens of predominantly myelosuppression and in particular granulocytopenia. CAP-treated patients had a higher frequency and severity of nausea and vomiting (25% vs 5%, p < 0.001) and alopecia (65% vs 2%, p < 0.001). INTERPRETATION: Fludarabine provided an effective and well-tolerated therapy for patients with advanced CLL, which compared favourably with CAP as one of the most effective standard regimens. In second-line therapy, fludarabine induced a significantly higher rate of complete and partial remissions, while in first-line therapy a significant prolongation of remission was obtained, which may translate into an improvement of overall survival.

Agranulocytosis↗
PubMed1996

Modulation by iron of hepatic microsomal and nuclear cytochrome P450, and cytosolic glutathione S-transferase and peroxidase in C57BL/10ScSn mice induced with polychlorinated biphenyls (Aroclor 1254).

Exposure of iron-loaded C57BL/10ScSn mice to the polychlorinated biphenyls (PCBs) mixture Aroclor 1254 in the diet (0.01%) for 5 weeks caused massive hepatic porphyria far greater than occurred with PCBs alone. This regime eventually causes hepatocellular carcinoma. Hepatic microsomal ethoxy-, pentoxy-, and benzyloxyresorufin dealkylase activities (respectively EROD, PROD, and BROD) catalyzed primarily by cytochrome P4501A1 and 2B isoenzymes were markedly induced after 2 weeks of diet (when no porphyria had developed) but showed little effect of iron. EROD activity in the nuclear membrane was also induced by the PCBs as was CYP1A1 protein when shown by immunoblotting. Nuclear dealkylase activities of PCBs-treated mice were considerably less than microsomal activities but were stimulated by iron pretreatment. The mechanism of the iron-enhanced toxicity may be due to oxidative damage associated with chronic induction of CYP1A1 isoforms. Lucigenin-enhanced chemiluminescence (CL) by microsomes and nuclear membranes was used as a method to estimate their potential to form reactive oxygen species. Despite CL being induced by PCBs it was less with microsomes from iron-treated mice. In a comparison of a variety of inducers of microsomal cytochrome P450 there was no correlation between inducer, uroporphyrogenic agent, and intensity of CL. On the other hand, cytosolic glutathione S-transferase (GST) activities with 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene (DCNB) as substrates, were also induced by the PCBs mixture, the induction with DCNB being synergistically potentiated by iron pretreatment. Complementary results were observed by immunocytochemistry using anti alpha-GST antibody. In contrast, total glutathione peroxidase activity and selenium-dependent glutathione peroxidase activity were depressed by PCBs but particularly in mice also administered iron. The results illustrate that PCBs not only induce CYP1A1 in microsomes but also in the nuclear membrane, which may be of significance in the mechanism of the iron-enhanced carcinogenicity of these chemicals. The iron-enhanced induction of GST with accompanying depletion of glutathione peroxidase provides evidence for oxidative processes induced in vivo by the PCBs.

Animals↗
PubMed1996

Subcellular location of the tetrapyrrole synthesis enzyme porphobilinogen deaminase in higher plants: an immunological investigation.

A recombinant plasmid, pArab8, harbouring the cDNA encoding the mature form of the tetrapyrrole synthesis enzyme porphobilinogen deaminase (EC 4.3.1.8; also known as hydroxymethylbilane synthase) from Arabidopsis thaliana (L.) Heynh. has been constructed, and used to transform Escherichia coli. The porphobilinogen deaminase protein from Arabidopsis was overexpressed in this strain, and purified to homogeneity (3000-fold) with a yield of 20%. Antibodies were raised against the purified plant enzyme, and used in Western blot analysis, immunoprecipitation of enzyme activity and immuno-gold electron microscopy. The results indicate that the enzyme is confined to plastids in both leaves and roots. The implications of this finding for plant tetrapyrrole synthesis are discussed.

Animals↗
PubMed1996

The Dai minority population of southwest China: heterogeneity of DR2-associated HLA-DRB1,DRB5,DQA1, and DQB1 haplotypes.

HLA-DR2 is the most common DR specificity (60.3%) identified in the Dai minority population of Xishuangbanna, Yunna Province, China. We characterized the DRB1, DRB5, DQA1, and DQB1 alleles of 44 unrelated DR2-positive individuals, 11 of whom (15%) were DR2 homozygous. Four DRB1 and four DRB5 alleles encoding DR2 were identified in this population. The most frequent DR2-associated DRB1 alleles were *1602 (gf = 0.164) and *1502 (gf = 0.151). DRB1*1501 (gf = 0.048) and a new allele designated DRB1*1504 (gf = 0.014) were also detected, but *1601 and *1503 were absent. The most frequent DR2-associated DRB5 alleles were *0101 (gf = 0.233) and *0102 (gf = 0.110). Nine different DR2-associated DR/DQ haplotypes were identified. The two most common DR2 haplotypes were DRB1*1602, DRB5*0101, DQA1*0102, DQB1*0502 (hf = 0.142) and DRB1*1502, DRB5*0102, DQA1*0101, DQB1*0501 (hf = 0.075). The new DRB1*1504 allele was found on a single haplotype: DRB1*1504, DRB5*0101, DQA1*0102, DQB1*0502 (hf = 0.017). The Dw2, Dw12, Dw21, and Dw22 haplotypes, present in many other Asian and Mongoloid populations, were not identified in this unique group. However, the Dai minority population is characterized by a relatively large number of diverse DR2 haplotypes and a new DRB1 allele encoding DR2.

China↗
PubMed1996

A phosphonate monoester hydrolase from Burkholderia caryophilli PG2982 is useful as a conditional lethal gene in plants.

A bacterial phosphonate monoester hydrolase was evaluated in plants as a conditional lethal gene useful for cell ablation and negative selection. Glyphosate is a potent herbicide whereas its phosphonate monoester derivative, glyceryl glyphosate, is approximately 50-fold less active. A phosphonate monoesterase gene (pehA) encoding an enzyme that hydrolyzes phosphonate esters including glyceryl glyphosate to glyphosate and glycerol was cloned from the glyphosate metabolizing bacterium, Burkholderia caryophilli PG2982. Constitutive expression of the pehA gene in Escherichia coli and Arabidopsis thaliana RLD had no observable phenotypic effects on growth and development. However, cells and plants expressing the pehA gene were killed when treated with glyceryl glyphosate. The phytotoxicity resulted from the hydrolysis of glyceryl glyphosate to glyphosate and subsequent inhibition of aromatic amino acid biosynthesis. As an example of tissue-specific cell ablation, floral sterility without vegetative toxicity was demonstrated by expressing the pehA gene using a tapetal-specific promoter and treating the mature plants with glyceryl glyphosate. A chromogenic phosphonate ester substrate, 5-bromo-4-chloro-indolyl phenylphosphonate, was used to monitor in situ expression of the pehA gene. The general utility of the pehA gene as a heterologous conditional lethal gene in plants is discussed.

Arabidopsis↗
PubMed1996

Isolation and expression of a host response gene family encoding thaumatin-like proteins in incompatible oat-stem rust fungus interactions.

Four cDNA clones (corresponding to tlp-1, -2, -3, and -4 genes) encoding thaumatin-like (TL), pathogenesis-related proteins were isolated from oat (Avena sativa) infected by an incompatible isolate Pga-1H of the oat stem rust fungus (Puccinia graminis f. sp. avenae). All four cDNA clones contained an open reading frame predicted to encode a 169-amino acid polypeptide with a signal peptide of 21 amino acids at the N-terminus, suggesting that these proteins are transported through a secretory pathway. The amino acid sequences revealed high homology among the four cDNA clones, 80 to 99% identity and 86 to 100% similarity. The tlp genes and several TL protein genes of certain cereals are clustered into a small group that is phylogenetically separate from the major group of TL protein genes of several plant species. In plants infected with the incompatible isolate Pga-1H, or an inappropriate isolate Pgt-8D of P. graminis f. sp. tritici, high levels of tlp gene transcripts accumulated at 42 to 48 h AI and thereafter when hypersensitive host cell death occurred and hyphal growth was inhibited, whereas in plants infected with a compatible isolate Pga-6A, relatively lower amounts of transcripts were detected. Overall, transcript levels were higher with tlp-1 than with the three other genes. Spray with a light mineral oil used as a spore carrier induced transient expression of tlp-1, -2, and -3 genes at 16 to 30 h AI which obscured the initial induction of the tlp genes in response to infection by the pathogens. In contrast, tlp-4 was induced very little by oil spray, so that induction was clearly observed in response to either compatible, incompatible, or inappropriate isolates at 24 to 30 h AI. Wounding leaves by either slicing or puncturing them strongly induced tlp-1 and tlp-3, moderately induced tlp-2, but had no effect on tlp-4. Taken together, the results showed that tlp genes displayed differential responses to oil spray, mechanical wounding, and pathogen infection and that the expression of tlp genes, especially tlp-1, in oat is associated with resistance reactions in response to infection by incompatible and inappropriate isolates of the stem rust fungi.

Amino Acid Sequence↗