The finding of a reciprocal whole-arm translocation t(X;12)(p10;p10) in association with atypical chronic myeloid leukaemia.

Atypical chronic myeloid leukaemia (aCML) belongs to the myeloproliferative/myelodysplastic category of haematological disease. Main characteristics are marked dysgranulopoiesis, bone marrow dysfunction and the failure to demonstrate the presence of the Philadelphia chromosome or BCR/ABL fusion gene normally associated with CML t(9;22)(q34;q11). It carries a poor prognosis with limited therapeutic options available. Most cases of aCML have one or more karyotypic abnormalities. We highlight a clinical presentation of aCML associated with an acquired reciprocal whole-arm translocation (WAT), t(X;12)(p10;p10), which to our knowledge has not yet been described. We also discuss how such a translocation might lead to tumorigenesis.

Integration of conventional cytogenetics, comparative genomic hybridisation and interphase fluorescence in situ hybridisation for the detection of genomic rearrangements in acute leukaemia.

AIMS: To screen for genomic imbalances in patients with acute leukaemia using conventional (G-banding) and molecular (comparative genomic hybridisation (CGH) and fluorescence in situ hybridisation (FISH)) methods to determine whether an integrative screening approach increases abnormality detection rate. METHODS: G-banded analysis was performed on unstimulated bone marrow (BM) or peripheral blood (PB) cells after short-term (24-hour) culture. CGH was performed on reference (control) and neoplastic (test patient) genomic DNA extracted from BM or PB samples. Interphase FISH (i-FISH) was selectively carried out at disease diagnosis on patients with acute lymphoblastic leukaemia and acute myeloid leukaemia using conventional methods. RESULTS: Genomic rearrangements were detected in 4, 7 and 6 patients using G-banding, CGH and i-FISH respectively. Discordance in results between G-banding, CGH and/or i-FISH was found in 7 of the 12 patients screened. G-banding and CGH, when used individually, detected a genomic imbalance/rearrangement in 33.3% and 58.3%, respectively, of the patients screened. However, when both screening methods were integrated, the abnormality detection rate increased to 66.7%. This detection rate increased further to 75.0% with the use of i-FISH screening. CONCLUSIONS: The advantages and disadvantages of using G-banding, CGH and i-FISH as either stand-alone or integrated screening methods for the detection and characterisation of genomic imbalances in acute leukaemia are clearly demonstrated. Abnormality detection rate significantly increased when an integrated screening approach was employed which could potentially provide valuable information for risk stratification in patients with acute leukaemia.

The prognostic value of FISH as an adjunct to conventional cytogenetics for the detection of cryptic gene rearrangements on chromosome 16. A retrospective investigation of 13 patients from Northern Ireland diagnosed with M4Eo acute myeloid leukaemia.

M4Eo acute myeloid leukaemia (AML) patients with the typical chromosome 16 abnormalities have a favourable prognosis. These subtle 16q22 gene rearrangements can be difficult to detect by conventional cytogenetic methods and if missed could lead to the incorrect assignment of prognostic group and hence subsequent treatment strategies. We retrospectively studied 13 patients diagnosed with M4Eo AML for such chromosome 16 abnormalities comparing conventional cytogenetic (G-banding) and molecular (FISH) methods. G-banded analysis detected only 2 patients with definite chromosome 16 abnormalities whereas FISH detected 4 patients, one with the typical inversion and three with the typical chromosome 16 translocation. FISH analysis also confirmed a false +ve G-banded result in one patient and a false -ve G-banded result in another patient. Finally, FISH confirmed a deletion of one chromosome 16 homologue in another patient indicating a poor prognosis. The overall survival of patients with the typical 16q22 rearrangements (n=4) was also significantly better (P=0.007) than patients with normal chromosome 16 homologues or having other numerical and/or structural abnormalities (n=9). This set of data shows that FISH is a more accurate method for the detection of cryptic 16q22 gene rearrangements and because of the prognostic implications has become a mandatory test along with conventional cytogenetics for all newly diagnosed M4Eo AML patients in Northern Ireland.

A partial cDNA sequence of the ovine insulin receptor gene: evidence for alternative splicing of an exon 11 region and for tissue-specific regulation of receptor isoform expression in sheep muscle, adipose tissue and liver.

Insulin is as integral and important to the management of metabolism in ruminants as it is in non-ruminants. The suggestion of a lowered ruminant sensitivity and/or responsivity to insulin may relate more to the insulin receptor than to the hormone itself. We screened an ovine cDNA library using degenerate primers and polymerase chain reaction (PCR) to detect and sequence a cDNA portion corresponding to exons 10, 11 and 12 of the human insulin receptor gene in which a 36 base pair (bp) segment (exon 11) is alternatively spliced to produce two distinct receptor isoforms differing in functional characteristics including binding affinity for insulin. The ovine cDNA segment (nucleotides 671 to 770) displayed 84, 84, and 78% nucleotide homology to equivalent segments from the human, rhesus monkey and rat respectively. Reverse transcription PCR (RT-PCR) of selected tissues (liver, m. longissimus dorsi, m. rectus capitis and omental, perirenal and subcutaneous fats) taken at slaughter from three male, pure Dutch Texel lambs (experiment 1) and five male Texel-Greyface crossbred lambs (experiment 2) revealed two mRNA products in each tissue (including spleen; experiment 2 only) corresponding to cDNAs of molecular sizes 161 and 197 bp -- a difference of 36 bp. Sequence alignment showed the 36 bp segment to be homologous to the alternatively spliced exon 11 region of the human insulin receptor gene and to be highly conserved with that from other species. The abundance of the exon 11(+) isoform in the purebred Texel genotype was significantly higher in liver than in perirenal fat and rectus capitis and longissimus dorsi skeletal muscles (P<0.05) and higher also than in subcutaneous and omental fats (P<0.01). There was, however, no difference in the abundance of the exon 11(+) isoform between the individual muscle and fat depots in this sheep genotype. The abundance of the exon 11(+) isoform in the crossbred Texel genotype was significantly higher in liver (P<0. 05) than in the muscles (rectus capitis, P<0.05; longissimus dorsi, P<0.001), all three fats (P<0.001) and spleen (P<0.001). In the crossbred genotype, the abundance of the exon 11(+) isoform was higher in skeletal muscle than in all three fat depots (P<0.001), in which the isoform abundance was similar. Altered ratios of expression of the two products of this alternative splicing event could determine tissue sensitivity and/or responsivity to insulin and provide a mechanism for the management of nutrient partitioning and nutrient utilisation between tissues which is fundamental to the growth of tissues and manipulation of carcass characteristics in meat-producing animals.

Parasympathetic effects on in vivo rat heart can be regulated through an alpha 1-adrenergic receptor.

A prejunctional mechanism involving an alpha 1-adrenergic receptor may exert control on the release of acetylcholine from parasympathetic nerve endings in the heart. To test this hypothesis in vivo, rats were prepared for electrical stimulation of the vagus nerves. Blood pressures and heart rates were monitored, and the animals were treated with alpha-agonists and alpha-antagonists. The alpha 1-selective agonist phenylephrine significantly attenuated vagally induced bradycardia in a dose-dependent fashion (ED50 = 19 micrograms/kg). This is consistent with the hypothesis that there is alpha-adrenergic inhibition of ACh release. In contrast, the alpha 2-selective agonist, BHT-920, caused no change in heart rate during vagal stimulation. The effects of phenylephrine to raise heart rate and blood pressure during vagal stimulation were blocked by the alpha 1-selective antagonist prazosin (ID50 approximately 1 microgram/kg) but not by the alpha 2-selective antagonists yohimbine and rauwolscine. This further supports an alpha 1 assignment to the prejunctional adrenergic receptor mechanism, which can regulate the release of acetylcholine from cardiac parasympathetic neurons.