The year 2000 problem: hiccough or approaching Armageddon.

The complexity of information technology systems has increased to approximate that of biological organisms, with a similar unpredictability of behaviour. With several million lines of code, a modern computer operating system, still can only be compared in complexity to a bacterial genome. However, just as unpredictable mutations continuously arise in the 3000 million haploid base pairs of human code and cause much misery and disease, undiscovered errors lie buried in the accumulated machine code which make up our world. As in human genetics, the difficulty is often distinguishing the harmless polymorphisms from the dangerous or lethal mutations. Similarly there is uncertainty about the impact of errors in data-handling code, which make up the "Year 2000 Problem". Over the remaining months it is vital that critical systems are checked for year 2000 compliance so as to avoid potentially serious disruption.

Massive blood transfusion in a tertiary referral hospital. Clinical outcomes and haemostatic complications.

OBJECTIVE: To determine blood products used, clinical outcomes and frequency of haemostatic complications of massive blood transfusion. DESIGN AND SETTING: Retrospective review of the medical records of patients receiving more than 10 units of blood in 24 hours at a tertiary referral hospital in 1993. PATIENTS: Forty-three patients fulfilled this criterion. The major reasons for massive transfusion were trauma (46%; 20 patients), gastrointestinal bleeding (21%; nine patients) and leaking abdominal aortic aneurysm (14%; six patients). MAIN OUTCOME MEASURES: Blood products used, platelet count ( < 50 x 10(9)/L in first 48 h), prothrombin time (PT) and activated partial thromboplastin time (APTT) (twice normal in first 48 h), microvascular bleeding, and survival. RESULTS: The 43 patients used 824 units of packed cells 15.2% of the total used in 1993), 457 units of fresh frozen plasma (FFP) (17.1% of the 1993 total) and 370 units of platelets (14.8% of the 1993 total). Overall, these patients consumed 16% of the total number of units of blood product used in 1993 for 1478 transfusion episodes. The overall survival rate was 60%. Severe coagulopathy occurred in 19 patients (44%) (mortality rate, 74%), and 13 (31%) had severe thrombocytopenia ( < 50 x 10(9)/L). There was no significant correlation between the severity of coagulopathy/thrombocytopenia and total units transfused, or between the age of the units of blood and development of coagulopathy or microvascular bleeding. CONCLUSIONS: Severe coagulopathy is common after massive transfusions. In the absence of clear correlation with the number of units transfused, "formula" replacement with plasma and platelets is unlikely to avoid the problem. Duration of tissue hypoperfusion and platelet consumption are likely to be more important than simple haemodilution of coagulation factors.

Comparative studies of nondeletional HPFH gamma-globin gene promoters.

The -198 T-->C and the -175 T-->C transitions involving the proximal gamma-globin gene promoter are associated with the hereditary persistence of fetal hemoglobin (HPFH) phenotype and have been demonstrated to increase promoter activity in erythroid cells using transient and stable transfection systems. The above base changes are thought to alter the binding of different transcription regulatory proteins. Another mutation of the proximal gamma-globin promoter, -158 C-->T, has been less clearly linked to the HPFH phenotype but has been associated with increased G gamma activity. In the present paper, the -198 T-->C, -175 T-->C and -158 C-->T mutations both singly and in various combinations were evaluated by an in vitro expression assay. gamma-Globin promoters were transfected by electroporation into K562 human erythroleukemia cells and their activity measured in a human growth hormone (hGH) reporter gene assay. A novel cotransfectant was used to assess transfection efficiency. Results confirmed the previously reported upregulation of gamma-globin activity with the -198 T-->C and -175 T-->C HPFH mutations and a cooperative effect on promoter activity when both these mutations are present in cis. No effect of the -158 C-->T mutation was seen either alone or in combination with the -175 T-->C and -198 T-->C mutations.

Human G gamma and A gamma globin gene constructs containing the 3' A gamma enhancer show persistent fetal expression in transgenic mice.

Transgenic mice were produced from two 13 kb constructs containing the fetal (gamma) globin genes. Each construct consisted of a G gamma globin gene linked to one of two alternative A gamma genes. The first construct contained a normal G gamma gene plus an A gamma gene with the -198 T-->C hereditary persistence of fetal haemoglobin (HPFH) mutation. In the second, a normal G gamma gene was linked to a A gamma gene with a -222 to -225 four base pair deletion in the promoter. This latter mutation has been associated with low A gamma expression in humans. Both A gamma genes in these constructs also contained the 3' flanking enhancer. The two different constructs showed expression throughout gestation from day 11 yolk sac, through the fetal period and for a variable time during the first three postnatal weeks. Thereafter, no expression of any of the gamma-globin genes was seen in adult erythroid tissues. Transcription from the normal G gamma and HPFH A gamma genes in the first construct paralleled each other in developmental timing, with a proportionate excess of A gamma more evident in later gestation. G gamma and A gamma mRNA transcripts from the normal G gamma + 4 bp deletional A gamma construct were unable to be distinguished because of a 3' G gamma-like conversion in the deletional A gamma gene. Combined gamma-globin expression from the two genes in this second construct was detectable until just after birth, as seen with the individual genes in the first construct.(ABSTRACT TRUNCATED AT 250 WORDS)

An A gamma globin promoter (four base-pair deletion) mutant shows linked polymorphic changes throughout the A gamma gene.

The A gamma fetal globin genes from a large Australian kindred with nondeletional A gamma hereditary persistence of fetal hemoglobin (HPFH) were cloned and sequenced. The -198 T----C mutation (British type HPFH) was demonstrated upstream of the A gamma gene on one allele. On the other allele, a 4-deletion was identified -222 to -225 bp upstream from the cap site. The 4-bp deletion allele was associated with a number of variations in the A gamma gene sequence: anA gamma T transition, in the second exon (T----C at +402 relative to the cap site); a HindIII polymorphism in the second intron; and a G gamma-like sequence in the 3' untranslated region (TCAC in place of CTCT, creating a SacI site). An association between the -222 to -225 deletion, the A gamma T polymorphism, and the second intron HindIII polymorphism has previously been reported. In addition, linkage of the HindIII polymorphism with the G gamma-like sequence in the 3' untranslated region of A gamma has also been described. The case described here is unique, with all four changes present in the one A gamma gene. It is also noteworthy because there is simultaneous occurrence of high (HPFH) and low (-222 to -225 deletion) expression mutants in the same patient. Despite the presence of the 4-bp deletion, the resulting hematological phenotype remained that of HPFH. When the 4-bp deletion promoter was studied in a K562-cell transient expression assay, there was found to be no statistically significant reduction in activity compared to the control A gamma promoter. The possible reasons for the observed differences between the in vivo and in vitro activity of this mutation are discussed.

Occurrence of the alpha thalassaemia-mental retardation syndrome (non-deletional type) in an Australian male.

The rare association of alpha thalassaemia and mental retardation has been described previously. Molecular studies of the alpha globin cluster in these cases have been heterogeneous, with some patients having large deletions while in others the alpha globin complex appears to be intact (non-deletional). The non-deletional cases form a distinct group whose features include severe mental retardation, haematological changes of haemoglobin H (Hb H) disease, developmental defects, and unusual patterns of inheritance. To date, five cases have been described with non-deletional alpha thalassaemia-mental retardation. We present here a further example of a young male of Northern European origin who appears to have the non-deletional form of the disease. Clinical features included severe mental retardation, Hb H disease, and developmental defects similar to those reported previously. DNA mapping, including pulsed field electrophoresis, showed no evidence of deletions within the alpha globin cluster. Karyotypic analysis indicated an increase in random breakage, which has been observed previously in one case of deletional alpha thalassaemia-mental retardation. Profuse Hb H bodies and Hb H on electrophoresis were consistent with Hb H disease. However, the latter was present at a relatively low level (1.6%) and, as well, the mean corpuscular volume (82.8 fl) and mean corpuscular haemoglobin (26.4 pg) were surprisingly high. Our findings are compared to other cases described with the non-deletional Hb H-mental retardation syndrome.

Complications associated with indwelling venous Hickman catheters in patients with hematological disorders.

During a 28 month period, 77 Hickman catheters were inserted in 66 patients with hematological disorders. Complete follow-up was possible for 72 catheter insertions. Catheters remained in situ for a median period of 77 days (range 5-474 days). Fourteen (19%) catheters required removal because of complications which included sepsis, blockage, or displacement. Catheter-related infection was the major complication and Staphylococcus epidermidis and diphtheroids (Corynebacterium species) were the organisms most commonly isolated.