Detection of myelodysplastic syndrome/ acute myeloid leukemia evolving from aplastic anemia in children, treated with recombinant human G-CSF

Backgrounds and Objectives: Recombinant human granulocyte colony-stimulating factor (G-CSF) has clear benefits in patients with severe neutropenia. However, recent reports of myelodysplastic syndrome/acute myeloid leukemia (t-MDS/AML) developing after treatment with immunosuppressants and G-CSF has raised concern over the use of this agent in patients with aplastic anemia. Design and Methods: We undertook a multi-institutional, non-randomized study of 112 children given a diagnosis of aplastic anemia, and then treated with different immunosuppressants with or without G-CSF. In each case, bone marrow specimens were tested at study entry and every 6 months for 3 years to detect t-MDS/AML, defined by stringent morphological and molecular/cytogenetic criteria. Incidence rates were calculated by the person-years statistical method. Results: As of December 2001, all eligible patients had been followed for a median of 3 years, and the G-CSF (+) group had received a median total G-CSF dose of 30,100 micrograms altogether, administered over a median of 4 months. Only one case of MDS developed among the G-CSF (+) patients (n=81), compared with three in the group receiving other agents (n=31). This isolated case was not associated with monosomy 7, the cytogenetic abnormality most often linked to G-CSF treatment. Incidence rates of MDS in the two groups were not significantly different (3.8 vs. 22.4 per 1,000 patient-years at risk, p=0.125). There were no cases of overt AML in either cohort. Interpretation and Conclusions: G-CSF therapy did not increase the risk of t-MDS/AML development in children with aplastic anemia over a median follow-up of 3.7 years     

Characterization of four N-3-thymidine adducts formed in vitro by the reaction of thymidine and butadiene monoxide

Four products were characterized from the reaction of thymidine with butadiene monoxide (BM), a known human mutagen and possible human carcinogen. These products were purified by HPLC and characterized as diastereomeric pairs of N-3-(1-hydroxy-3-buten-2-yl)thymidine and N-3- (2-hydroxy-3-buten-1-yl)thymidine based upon their UV spectra, 1H NMR and fast atom bombardment mass spectra. Incubation of thymidine with an excess of BM at pH 7.4 and 37 degrees C allowed calculation of the pseudo-first-order kinetic rate constants for the adduct formation, but when these rate constants were compared with the rates we previously determined with guanosine, adenosine and deoxycytidine, the results suggested a lower reactivity with thymidine in comparison with the other nucleosides. When incubations were carried out at lower BM concentrations, the formation of adducts appeared to be linearly dependent on BM concentration. The four thymidine adducts were completely stable for 1 week when incubated at 37 degrees C in pH 7.4 phosphate buffer. These results suggest that the interactions of BM with thymidine may play a role in the molecular mechanisms of mutagenesis and carcinogenesis of BM.      

Truncal site and detoxifying enzyme polymorphisms significantly reduce time to presentation of further primary cutaneous basal cell carcinoma

Basal cell carcinoma (BCC) is the commonest cancer in Caucasians. Its incidence is rising and many patients develop multiple primary tumours at separate sites. Factors determining time between first primary tumour presentation and the next new primary lesion are unclear. We used Cox's proportional hazards model to study, in 856 Caucasians, the influence of tumour site, individual characteristics and polymorphism in glutathione S-transferase (GSTM1, GSTT1) and cytochrome P450 (CYP2D6, CYP1A1) loci on time to next primary tumour presentation. More than one tumour at first presentation (P <0.0001, hazard ratio 2.72) and GSTT1 null (P = 0.028, hazard ratio 1.74) were associated with decreased time to next primary tumour presentation. Significant two- factor interactions, corrected for number of tumours at presentation, were identified between a truncal tumour at first presentation and each of male gender, GSTM1 null and CYP2D6 EM (P <0.003, hazard ratios 3.09- 3.82). In each of these cases, all patients with the risk combination demonstrated further separate tumours within 5 years of first presentation. Thus, patients with a truncal tumour at first presentation, especially males and those presenting with more than one lesion have a significantly decreased time to presentation of further tumours and should receive more meticulous follow-up. Polymorphism in GSTM1 and CYP2D6 also influences the rate of new primary tumour accrual giving insights into the link between ultraviolet exposure and multiple tumour development.      

Patterns of chloroform-induced regenerative cell proliferation in BDF1 mice correlate with organ specificity and dose-response of tumor formation

It has been reported that chloroform administered to BDF1 mice by inhalation for 2 years at concentrations of 5, 30 or 90 p.p.m. for 6 h/day, 5 days/week induced an increase in renal cell tumors in male but not female mice exposed to the doses of 30 and 90 p.p.m. A small increase in liver tumors was statistically significant in the female mice at 90 p.p.m. if the incidences of carcinomas and adenomas were combined. Because chloroform is not a DNA reactive mutagen, a 13-week time-course and dose-response study was conducted under conditions of the original bioassay to examine whether regenerative cell proliferation was an underlying mechanism of carcinogenesis. Mice were given bromodeoxyuridine via infusion during the last 3.5 days prior to necropsy to label cells in S-phase. Chloroform induced pathology and regenerative cell proliferation, measured as the labeling index (LI, percentage of cells in S-phase), were assessed microscopically and immunohistochemically. Male mice exposed to 30 and 90 p.p.m. exhibited a dose-dependent increase in regenerating tubules within the renal cortex and up to a 31-fold increase in LI. No renal lesions or increased LI were observed in females. Increased centrilobular to midzonal hepatocyte degeneration and vacuolation and a 7-fold increase over controls in the hepatocyte LI were observed in the female mice at 90 p.p.m. at 13 weeks. Males exhibited similar pathology, but the increase in LI was not sustained. The observed correlations between cytolethality and regenerative cell proliferation with tumor formation supports extensive evidence that chloroform induces cancer via a non- genotoxic-cytotoxic mode of action. A concentration of 5 p.p.m. is the no-observed-adverse-effect level for nephrotoxicity, cell proliferation and cancer. An appropriate safety factor applied to this value is a straightforward approach to cancer risk assessment that is consistent with the mode of action of chloroform.      

The natural history of anterior cruciate ligament reconstruction using patellar tendon autograft

The purpose of this study was to review the results of ACL reconstruction using a patellar tendon graft placed ‘over the top’ plus a Macintosh lateral tenodesis, examining changes in knee laxity and functional status with increasing time. There were 74 patients operated on over an 11 year period, and divided into four groups for analysis according to postoperative time. There was a significant and progressive increase in side-to-side laxity difference with time, although functional status did not change significantly, indicating a lack of correlation between objective clinical tests and subjective findings. The highest Lysholm, Tegner and IKDC scores were at 4–5 years after operation, when 60% of patients were at their pre-injury level of sports activity. However, there was always a very significant difference between actual and desired Tegner activity levels for the group as a whole. While there was a significant correlation between degenerative changes and the time between injury and reconstruction, there was no correlation with postoperative time: this provides evidence that ACL reconstruction can protect the knee from later degeneration.     

The influence of the cultural climate of the training environment on physicians' self-perception of competence and preparedness for practice

Background  

In current supervisory practice, the learning environment in which the training of specialist registrars (SpRs) takes place is important. Examples of such learning environments are the hospital settings and/or geographical locations where training occurs. Our objective was to investigate whether the cultural climate of different learning environments influences physicians' perceived level of competence and preparedness for practice.     

High frequency of IgE receptor FcεRIß variant (Leu181/Leu183) in Kuwaiti Arabs and its association with asthma

The presence of IgE receptor FcεRIβ polymorphism (181/183) was investigated in Kuwaiti asthmatic patients and controls using an allele refractory mutation screening (ARMS) test. The variant sequence (Leu181/Leu183) was detected in 72% (320/442) chromosomes analysed. Homozygous LL genotype was detected in 48% (46/96) asthmatic subjects compared to 31% (39/125) in non-asthmatics. In 11/52 families mothers of the asthmatic children were themselves asthmatic and 3/11 asthmatic mothers had homozygous LL genotype. 80% of the homozygous LL asthmatics showed a positive skin prick test (SPT) compared with 28% of non-asthmatics with the same genotype. In heterozygous NL asthmatics a positive SPT was found in 60% cases compared to 17% in non asthmatics with the same genotype. The incidence of hay fever (HF) and eczema (E) was also found to be higher in homozygous LL asthmatics compared with the non-asthmatics with the same genotype. This study reports a high prevalence of IgE receptor FcεRIβ variants in Kuwaiti Arabs compared with British, Australian and Austrian populations studied before. The association of Leu181/Leu183 variant with asthma in Kuwaitis underlines its significance as a risk factor in manifesting the clinical phenotype in this population.     

Autosomal recessive retinitis pigmentosa and cone-rod dystrophy caused by splice site mutations in the Stargardt's disease gene ABCR

Ophthalmological and molecular genetic studies were performed in a consanguineous family with individuals showing either retinitis pigmentosa (RP) or cone-rod dystrophy (CRD). Assuming pseudodominant (recessive) inheritance of allelic defects, linkage analysis positioned the causal gene at 1p21-p13 (lod score 4.22), a genomic segment known to harbor the ABCR gene involved in Stargardt's disease (STGD) and age- related macular degeneration (AMD). We completed the exon-intron structure of the ABCR gene and detected a severe homozygous 5[prime] splice site mutation, IVS30+1G->T, in the four RP patients. The five CRD patients in this family are compound heterozygotes for the IVS30+1G- >T mutation and a 5[prime] splice site mutation in intron 40 (IVS40+5G- >A). Both splice site mutations were found heterozygously in two unrelated STGD patients, but not in 100 control individuals. In these patients the second mutation was either a missense mutation or unknown. Since thus far no STGD patients have been reported to carry two ABCR null alleles and taking into account that the RP phenotype is more severe than the STGD phenotype, we hypothesize that the intron 30 splice site mutation represents a true null allele. Since the intron 30 mutation is found heterozygously in the CRD patients, the IVS40+5G->A mutation probably renders the exon 40 5[prime] splice site partially functional. These results show that mutations in the ABCR gene not only result in STGD and AMD, but can also cause autosomal recessive RP and CRD. Since the heterozygote frequency for ABCR mutations is estimated at 0.02, mutations in ABCR might be an important cause of autosomal recessive and sporadic forms of RP and CRD.