Ototoxicity induced by once-daily gentamicin.
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Adult↗
Biomedical subjects
A G Smith
Publications and source records attributed to A G Smith.
Increased skin tumorigenesis in mice lacking pi class glutathione S-transferases.
The activity of chemical carcinogens is a complex balance between metabolic activation by cytochrome P450 monooxygenases and detoxification by enzymes such as glutathione S-transferase (GST). Regulation of these proteins may have profound effects on carcinogenic activity, although it has proved impossible to ascribe the observed effects to the activity of a single protein. GstP appears to play a very important role in carcinogenesis, although the precise nature of its involvement is unclear. We have deleted the murine GstP gene cluster and established the effects on skin tumorigenesis induced by the polycyclic aromatic hydrocarbon 7, 12-dimethylbenz anthracene and the tumor promoting agent 12-O-tetradecanoylphorbol-13-acetate. After 20 weeks, a highly significant increase in the number of papillomas was found in the GstP1/P2 null mice [GstP1/P2(-/-) mice, 179 papillomas, mean 9.94 per animal vs. GstP1/P2(+/+) mice, 55 papillomas, mean 2.89 per animal, (P < 0.001)]. This difference in tumor incidence provides direct evidence that a single gene involved in drug metabolism can have a profound effect on tumorigenicity, and demonstrates that GstP may be an important determinant in cancer susceptibility, particularly in diseases where exposure to polycyclic aromatic hydrocarbons is involved, for instance in cigarette smoke-induced lung cancer.
9,10-Dimethyl-1,2-benzanthracene↗
Uroporphyria produced in mice by iron and 5-aminolaevulinic acid does not occur in Cyp1a2(-/-) null mutant mice.
In the present study we have investigated the putative requirement for the cytochrome P-450 isoform CYP1A2 in murine uroporphyria, by comparing Cyp1a2(-/-) knockout mice with Cyp1a2(+/+) wild-type mice. Uroporphyria was produced by injecting animals with iron-dextran and giving the porphyrin precursor 5-aminolaevulinic acid in the drinking water. Some animals also received 3-methylcholanthrene (MC) to induce hepatic CYP1A2. In both protocols, uroporphyria was elicited by these treatments in the Cyp1a2(+/+) wild-type mice, but not in the null mutant mice. Uroporphyrinogen oxidation activity in hepatic microsomes from untreated Cyp1a2(+/+) mice was 2.5-fold higher than in Cyp1a2(-/-) mice. Treatment with MC increased hepatic CYP1A1 in both mouse lines and hepatic CYP1A2 only in the Cyp1a2(+/+) line, as determined by Western immunoblotting. MC increased hepatic ethoxy- and methoxy-resorufin O-dealkylase activities in both mouse lines, but increased uroporphyrinogen oxidation activity in the Cyp1a2(+/+) wild-type mice only. These results indicate the absolute requirement for hepatic CYP1A2 in causing experimental uroporphyria under the conditions used.
Aminolevulinic Acid↗
Patients with truncal basal cell carcinoma represent a high-risk group.
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Basal Cell Carcinoma↗
Multiple blisters in a young boy. Linear IgA disease of childhood (LADC). (Chronic bullous dermatosis of childhood).
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Child, Preschool↗
Quality of life--an overdue clinical measurement in multiple myeloma.
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Antineoplastic Agents↗
Crystal structure of aspartate decarboxylase at 2.2 A resolution provides evidence for an ester in protein self-processing.
The structure of L-aspartate-alpha-decarboxylase from E. coli has been determined at 2.2 A resolution. The enzyme is a tetramer with pseudofour-fold rotational symmetry. The subunits are six-stranded beta-barrels capped by small alpha-helices at each end. The active sites are located between adjacent subunits. The electron density provides evidence for catalytic pyruvoyl groups at three active sites and an ester at the fourth. The ester is an intermediate in the autocatalytic self-processing leading to formation of the pyruvoyl group. This unprecedented structure provides novel insights into the general phenomenon of protein processing.
Amino Acid Sequence↗
Acute leukaemia in Jehovah's Witnesses.
The refusal of Jehovah's Witnesses with leukaemia to accept transfusion provides a major clinical challenge because of the myelosuppressive effects of chemotherapy. Experience in treating five such patients is described. Two patients with acute lymphoblastic leukaemia (ALL) achieved remission following chemotherapy, the first without transfusion support, the second, a minor, receiving transfusion under a court order: the first patient remains in remission 5 years later, whereas the second subsequently relapsed and died. Of three patients with acute myeloid leukaemia (AML), two received chemotherapy: one died of anaemia during induction chemotherapy whereas the second eventually consented to transfusion but died of refractory leukaemia. The third patient died of anaemia despite erythropoietin. We feel Jehovah's Witnesses should not be denied antileukaemic therapy if they fully understand the risks involved. Minimizing phlebotomy, use of antifibrinolytic agents and growth factors may make chemotherapy feasible, especially in ALL where remission may be induced with less myelosuppressive agents. The outlook for those with AML treated with conventional chemotherapy appears poor; alternative approaches to treatment should be considered in these patients.
Adolescent↗
Two different genes encode ferrochelatase in Arabidopsis: mapping, expression and subcellular targeting of the precursor proteins.
Ferrochelatase is the last enzyme of haem biosynthesis. We have isolated 27 independent ferrochelatase cDNAs from Arabidopsis thaliana by functional complementation of a yeast mutant. Twenty-two of these cDNAs were similar to a previously isolated clone, AF3, and although they varied in length at the 5' and 3' ends, their nucleotide sequences were identical, indicating that they were derived from the same gene (ferrochelatase-I). The remaining five cDNAs all encoded a separate ferrochelatase isoform (ferrochelatase-II), which was 69% identical at the amino acid level to ferrochelatase-I. Using RFLP analysis in recombinant inbred lines, the ferrochelatase-I gene was mapped to chromosome V and that for ferrochelatase-II to chromosome II. Northern analysis showed that both ferrochelatase genes are expressed in leaves, stems and flowers, and expression in the leaves is higher in the light than in the dark. However, in roots only ferrochelatase-I transcripts were detected. High levels of sucrose stimulated expression of ferrochelatase-I, but had no effect, or repressed slightly, the expression of the ferrochelatase-II isoform. Import experiments into isolated chloroplasts and mitochondria showed that the ferrochelatase-II gene encodes a precursor which is imported solely into the chloroplast, in contrast to ferrochelatase-I which is targeted to both organelles. The significance of these results for haem biosynthesis and the production of haemoproteins, both within the plant cell and in different plant tissues, is discussed.
Amino Acid Sequence↗
Is the timing of post-vasectomy seminal analysis important?
OBJECTIVE: To review the practice in two hospitals with differing protocols in the timing of seminal analysis after vasectomy. PATIENTS AND METHODS: The results from 245 vasectomies carried out at Hospital A, where semen was assessed 3 months after vasectomy, were reviewed and compared with those from 100 consecutive vasectomies at Hospital B, where semen was assessed 6 months after vasectomy. The results of seminal analysis at Hospital A were also audited after changing to the 6-month protocol. The patients' preferences for the timing of seminal analysis were also obtained. RESULTS: Of the 245 patients at Hospital A, 58 (24%) failed to provide samples, leaving 187 (76%) for evaluation; 528 samples were examined (mean 2.8 per patient, range 1-13). The first sample was positive in 36 (19.3%) and the second positive in 10 (5.3%), the first being negative. Four (2%) patients had persistent spermatozoa at 6 months, one subsequently undergoing exploration. Thirty-one (17%) patients provided further samples despite providing two consecutive clear ones. At Hospital B, 24 (24%) patients failed to provide samples; 10 (13%) patients had persistent spermatozoa at 6 months and live spermatozoa were detected in one patient's samples. All eventually produced clear samples, with none requiring exploration. After changing the protocol, 87 vasectomies were performed, with 18 (21%) patients failing to provide samples; seven (10%) of the samples collected showed occasional nonmotile spermatozoa at 6 months in either the first, second or both samples, with all samples clear by 8 months after vasectomy. CONCLUSIONS: The complete disappearance of spermatozoa after vasectomy takes longer than is generally believed and we therefore suggest that given adequate counselling, seminal analysis 6 months after vasectomy is cost-effective and in the patient's interest.
Humans↗
Susceptibility to melanoma: influence of skin type and polymorphism in the melanocyte stimulating hormone receptor gene.
Allelic variation at the melanocyte stimulating hormone receptor (MC1R) gene has been linked with sun-sensitive skin types, suggesting it is a susceptibility candidate for melanoma. We determined the frequency of the val92met, asp294his, and asp84glu MC1R alleles in 190 Caucasian controls and 306 melanoma cases and studied their association with skin type and hair color. The percentage of controls with at least one val92met, asp294his, or asp84glu allele was 17.3%, 6.8%, and 3.5%, respectively. Individually, frequencies of the val92met, asp294his, or asp84glu alleles in the controls with skin types 3 and 4 were similar to those with skin types 1 and 2. Trend analysis, however, did identify an association (exact p = 0.048, two-sided test) between skin type and MC1R variants in the group comprising all controls with any one or more of these alleles. There was no association between MC1R alleles and hair color. Allele frequencies were not different in melanoma cases and controls. There were no associations between skin types and the proportion of cases with the asp294his or asp84glu alleles, though the association between skin type and the val92met allele approached significance (exact p = 0.09, two-sided test). Unexpectedly, in the group comprising all cases with one or more variant alleles, the proportion of subjects with variant alleles increased with skin types associated with tanning rather than burning, although trend analysis showed that this association did not quite reach statistical significance (exact p = 0.08, two-sided test). Asp84glu (but not val92met or asp294his) variant alleles were more common in subjects with blonde hair, although the relationship between the asp84glu allele and hair color did not achieve statistical significance (chi(2)3 = 6.16, exact p = 0.10). We interpret the data presented as indicating that polymorphism at MC1R does not appear a major determinant of skin type, at least in terms of these allelic variants. Furthermore, considered alone, these alleles are not susceptibility candidates for malignant melanoma.
Adult↗
The LabBase system for data management in large scale biology research laboratories.
MOTIVATION: The development of laboratory information management systems (LIMSs) for large scale biology research projects can be a challenging problem. Many such projects generate complex datasets via complex procedures that undergo continuous refinement. A key software challenge is to simplify the database-development task so that databases can be built and modified quickly enough to keep pace with changing project-requirements. RESULTS: LabBase extends the facilities offered by relational database systems to simplify the task of creating databases for large scale biology research projects. LabBase provides a structural object data model, similar to ACEDB, and adds to this the concepts of Materials, Steps, and States: Materials are objects representing the identifiable things that participate in a laboratory protocol; Steps are objects reporting the results of a laboratory or analytical procedure; and States are objects denoting places in a laboratory protocol. The system provides a data definition language for succinctly defining laboratory databases, and operations for conveniently storing and retrieving data in such databases. The system also provides support for workflow management. LabBase is implemented in Perl5 and provides a natural interface for laboratory application programs written in Perl. AVAILABILITY: The software is freely available. Contact the authors. CONTACT: nat@jax.org
Computational Biology↗
Redox regulation of Brn-2/N-Oct-3 POU domain DNA binding activity and proteolytic formation of N-Oct-5 during melanoma cell nuclear extraction.
Reversible oxidation sensitivity of N-Oct-3 DNA binding activity was seen when melanoma extracts and recombinant Brn-2 protein were treated with a variety of metals, hydrogen peroxide and the cysteine disulphide bond forming agent diamide. Western blot analysis of diamide-oxidized N-Oct-3 protein indicated that this was likely to be due to intramolecular disulphide bonding. The potential role of oxidative loss of N-Oct-3 DNA binding activity is discussed in relation to redox changes that may occur during the early phase of apoptosis in neuronal cell lines and tissues. Brn-2 C-terminal antibody Western blot analysis of melanoma cell line nuclear extracts prepared using a combination of sodium dodecyl sulphate and NP-40 detergent cell lysis procedures demonstrated the formation of N-Oct-5 DNA binding activity via N-terminal proteolytic clipping of Brn-2/N-Oct-3.
Animals↗
Chromosomal linkage analysis of porphyria in mice induced by hexachlorobenzene-iron synergism: a model of sporadic porphyria cutanea tarda.
Genetic susceptibility to toxic chemicals is of major importance but most studies concentrate on candidate genes and searches for unknown susceptibility genes are uncommon. Human sporadic porphyria cutanea tarda is usually precipitated by alcohol, oestrogens, hepatitis viruses, HIV or haemodialysis. The mechanism is not known but there is a role for iron metabolism and an underlying genetic predisposition is suspected. A similar porphyria in humans has also been caused by hexachlorobenzene. These human porphyrias can be modelled in iron-loaded mice exposed to hexachlorobenzene, in which C57BL/10ScSn is a prototype susceptible strain whereas DBA/2 mice are extremely resistant. A search for susceptibility genes was undertaken using complex trait analysis with DNA microsatellite markers of 'high' and 'low' responders from an F2 intercross. Correlation of markers with susceptibility, defined as accumulation of uroporphyrin in the liver, was assessed by chi-squared test for the proportion of C57BL/10ScSn and DBA/2 alleles present. Susceptibility loci on chromosomes 12, 14 and 17 were identified. Further analysis of markers on chromosomes 14 and 17 by MAPMAKER/EXP and MAPMAKER/QTL gave LOD scores of 7.3 and 3.6, respectively. Typing of chromosome 12 for the Ahr gene, using a restriction fragment length polymorphism distinguishing between the b-1 and d alleles, gave significant but not perfect linkage. However, no strong association between alleles or expression of Cyp1a1/2 genes, regulated by Ahr, and susceptibility for porphyria was detected. The results demonstrate that the porphyria induced by hexachlorobenzene in C57BL/10ScSn mice is a complex trait determined by at least three genes, which may be of relevance to susceptibility in the development of sporadic porphyria cutanea tarda and unknown aspects of liver damage.
Animals↗
Multiple genes encoding the conserved CCAAT-box transcription factor complex are expressed in Arabidopsis.
The CCAAT motif is found in the promoters of many eukaryotic genes. In yeast a single complex of three proteins, termed HAP2, HAP3, and HAP5, binds to this sequence, and in mammals the three components of the equivalent complex (called variously NF-Y, CBF, or CP1) are also represented by single genes. Here we report the presence of multiple genes for each of the components of the CCAAT-binding complex, HAP2, 3,5, from Arabidopsis. Three independent Arabidopsis HAP subunit 2 (AtHAP2) cDNAs were cloned by functional complementation of a yeast hap2 mutant, and two independent forms each of AtHAP3 and AtHAP5 cDNAs were detected in the expressed sequence tag database. Additional homologs (two of AtHAP3 and one of AtHAP5) have been identified from available Arabidopsis genomic sequences. Northern-blot analysis indicated ubiquitous expression for each AtHAP2 and AtHAP5 cDNA in a range of tissues, whereas expression of each AtHAP3 cDNA was under developmental and/or environmental regulation. The unexpected presence of multiple forms of each HAP homolog in Arabidopsis, compared with the single genes in yeast and vertebrates, suggests that the HAP2,3,5 complex may play diverse roles in gene transcription in higher plants.
Amino Acid Sequence↗
Definition of the gene encoding the minor histocompatibility antigen HA-1 and typing for HA-1 from genomic DNA.
Recipient mismatching for the minor histocompatibility antigen HA-1 has been associated with acute graft-versus-host disease after allogeneic marrow transplantation. Two polymorphic nucleotides near an exon-intron junction of the gene encoding this minor histocompatibility antigen have been identified. In this study, we determined the genomic DNA sequence of the intron downstream from this polymorphic exon. Based on this sequence, primers were designed to amplify the genomic HA-1 gene sequence, and analysis of restriction fragment length polymorphisms was used to assign the HA-1 genotypes of 160 unrelated probands and a paired sibling for each proband. Among probands, the HA-1H allele frequency was 0.441, and the HA-1R allele frequency was 0.559. The distribution of HA-1 genotypes showed close fit with Hardy-Weinberg equilibrium. Likewise, the number of sibling pairs with disparity for HA-1 alleles showed close fit with predictions based on Hardy-Weinberg equilibrium. These results provide a simple and well validated method for future studies correlating HA-1 disparity with clinical outcome after allogeneic marrow transplantation.
Alleles↗
Interaction between iron metabolism and 2,3,7,8-tetrachlorodibenzo-p-dioxin in mice with variants of the Ahr gene: a hepatic oxidative mechanism.
The binding of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) with the aryl hydrocarbon (AH) receptor and subsequent changes in gene expression have been studied intensively, but the mechanisms by which these lead to toxicity are unclear. We investigated the influence of iron, previously implicated in TCDD-induced hepatic porphyria, in mice with alleles of Ahr that encode receptors with varied affinity for TCDD. The administration of iron to Ahrb-1 C57BL/6J (AH-responsive) mice before a single dose of TCDD (75 micrograms/kg) markedly potentiated not only the hepatic porphyria but also general hepatocellular damage and elevation of plasma hepatic enzymes. The formation of hydroxylated and peroxylated derivatives of uroporphyrins formed from uroporphyrinogen and the induction of a mu-glutathione transferase (GST) were consistent with the operation of an oxidative mechanism. In a comparison of C57BL/6J mice with Ahrb-2 BALB/c (AH-responsive) and Ahrd SWR and DBA/2 (AH-nonresponsive) mice, iron overcame the weak hepatic porphyria and toxicity responses in BALB/c and SWR strains but not in DBA/2. CYP1A isoforms are strongly implicated in the mechanism of porphyria, but activities were lowered by 20-30% with iron treatment, and a comparison of levels between strains did not fully account for the resistance of DBA/2 mice. Studies with the use of gel shift assays and cytosolic aconitase of the capacity of the iron regulatory protein controlling the translation of some iron metabolism proteins showed a significant difference between C57BL/6J and DBA/2 mice after the administration of TCDD. We conclude that iron potentiates both the hepatic porphyria and toxicity of TCDD in susceptible mice in an oxidative process with disturbance of iron regulatory protein capacity. Iron even overcomes the AH-nonresponsive Ahrd allele in the SWR strain but not in DBA/2 mice, which remain resistant.
Alleles↗
A Schwann cell mitogen accompanying regeneration of motor neurons.
Motor neurons are the only adult mammalian neurons of the central nervous system to regenerate following injury. This ability is dependent on the environment of the peripheral nerve and an intrinsic capacity of motor neurons for regrowth. We report here the identification, using a technique known as messenger RNA differential display, of an extracellular signalling molecule, previously described as the pancreatic secreted protein Reg-2, that is expressed solely in regenerating and developing rat motor and sensory neurons. Axon-stimulated Schwann cell proliferation is necessary for successful regeneration, and we show that Reg-2 is a potent Schwann cell mitogen in vitro. In vivo, Reg-2 protein is transported along regrowing axons and inhibition of Reg-2 signalling significantly retards the regeneration of Reg-2-containing axons. During development, Reg-2 production by motor and sensory neurons is regulated by contact with peripheral targets. Strong candidates for peripheral factors regulating Reg-2 production are cytokines of the LIF/CNTF family, because Reg-2 is not expressed in developing motor or sensory neurons of mice carrying a targeted disruption of the LIF receptor gene, a common component of the receptor complexes for all of the LIF/CNTF family.
Animals↗