Gene-directed enzyme prodrug therapy: quantitative bystander cytotoxicity and DNA damage induced by CB1954 in cells expressing bacterial nitroreductase

Clones of human colon carcinoma (WiDr), ovarian carcinoma (SK-OV-3), and Chinese hamster V79 cells expressing the nitroreductase enzyme (NR) from E. coli B were 52-, 225- and 177-fold respectively more sensitive to a 24-h incubation with the prodrug 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB1954) than the parent lines. The IC50s of non-NR-expressing bystander cells were measured in the presence of differing proportions of NR-expressing cells. The shift in IC50 was used to calculate a value for the bystander effect, termed the transmission efficiency (TE), which is the decrease in IC50 due to bystander effect as a percentage of the maximum decrease possible. The percentage of NR-expressing cells for which the TE was 50%, (the TE50) is a single datum of bystander efficacy. WiDr and V79 cell lines, had a similar TE50 of approximately 2%. SK-OV-3 gave a lower value of 0.3%. These TE50 correlate with concentrations of cytosolic NR activity, which is distinguished from endogenous DT diaphorase activity by kinetic differences. A novel method is described which enables both DNA crosslinks and drug-induced single-strand breaks to be simultaneously quantified in a sedimentation assay. Using this technique, bystander DNA damage was demonstrated in V79 cells, of approximately 50% of that in activator cells.

Rapid purification and characterisation of HIV-1 reverse transcriptase and RNaseH engineered to incorporate a C-terminal tripeptide alpha-tubulin epitope

The C-termini of p66 and p51 forms of HIV-1 reverse transcriptase have been engineered to contain a Glu-Glu-Phe sequence recognized by a monoclonal antibody to alpha-tubulin, YL1/2. Mutated RTs were purified in a single step using peptide elution from columns of immobilized YL1/2. The known sequence requirements of the YL1/2 epitope are consistent with protein eluting from the column with an intact C-terminus. Kinetic parameters of these mutated RTs are essentially unchanged from wild-type enzyme. The p15 RNaseH domain has been purified using this method and shown to have low enzyme activity compared to the parental p66 subunit.

Inhibition of influenza virus transcription by 2'-deoxy-2'-fluoroguanosine

The nucleoside analog 2'-deoxy-2'-fluoroguanosine (2'-fluorodGuo) is phosphorylated by cellular enzymes and reversibly inhibits influenza virus replication in chick embryo cells within the first 4 h of infection. RNA hybridization studies revealed that primary and secondary transcription of influenza virus RNA were blocked at a compound concentration of 10 microM, but no inhibition of cell protein synthesis was seen even at high compound concentrations (200 microM). In vitro, the triphosphate of 2'-fluorodGuo is a competitive inhibitor of influenza virus transcriptase activity from disrupted virus, with a Ki of 1.0 microM. The cellular polymerases DNA polymerase alpha and RNA polymerase II were only weakly inhibited or were insusceptible to 2'-fluorodGTP. In kinetic studies with the influenza virus transcriptase, 2'-fluorodGTP, in the absence of GTP, blocked elongation of the virus RNA chain. Similarly, by using purified ribonucleoprotein complexes it was found that the addition of a single nucleotide of 2'-fluorodGTP to the virus RNA caused chain termination, which resulted in the blockage of further virus transcription. Furthermore, the specificity for influenza virus transcriptase was confirmed when the transcriptase from partially resistant virus was found to be 10-fold less susceptible to 2'-fluorodGTP (Ki = 13.1 microM).

Dietary survey of diabetics

This study of 168 diabetic children from Tyneside and Teeside aimed to record what the children actually ate and to compare this with both their prescribed diet and current recommendations. The amounts of energy consumed were similar to those expected of non-diabetic children, but the components of the diabetic children's diets were different, consisting of more fat and fibre, but less sugars and carbohydrates. They ate more carbohydrate than prescribed but less than current recommendations as there was a shortfall between the amount prescribed and that suggested in the recommendations. Diabetic control was related to the amount of fibre consumed and to compliance with the prescribed diet, but not to the proportion of energy taken as carbohydrate. The insulin dose was slightly lower in those children eating more fibre.

Isolation of the ERG2 gene, encoding sterol delta 8-->delta 7 isomerase, from the rice blast fungus Magnaporthe grisea and its expression in the maize smut pathogen Ustilago maydis

The Magnaporthe grisea ERG2 gene, encoding delta 8-->delta 7 sterol isomerase, was isolated from a genomic library by heterologous hybridization to a fragment of the Ustilago maydis ERG2 gene. The isolated gene contained a reading frame of 745 bp which encoded a protein of 221 amino acids. The coding region was interrupted by a single putative 79-bp-long intron. The deduced amino-acid sequence exhibited similarity to the ERG2 gene products of U. maydis and of Saccharomyces cerevisiae, particularly in the central region of the proteins. The NH2-terminal of all three proteins contained a long stretch of amino acids that were strongly hydrophobic, suggesting that they may function by anchoring the protein to a membrane surface. The M. grisea ERG2 gene complemented a U. maydis deletion mutant in which the ERG2 gene had been removed using a one-step gene replacement procedure. The delta 8-->delta 7 sterol isomerase produced by the M. grisea ERG2 gene exhibited a level of sensitivity to the sterol biosynthesis inhibitor, tridemorph, similar to that of the enzyme derived from the U. maydis ERG2 gene.

Circulating lipids and glycaemic control in insulin dependent diabetic children

The prevalence of dyslipidaemia in children with insulin dependent diabetes mellitus (IDDM) and its relation to glycaemic control was studied in a group of 51 diabetic children and a control population of 132 schoolchildren. The prevalence of dyslipidaemia in the fasting state was increased in the diabetic group (39%) compared with control subjects (17%). Serum cholesterol concentration alone was raised in 25% of diabetic subjects while serum cholesterol and triglycerides were raised in 14%, compared with 16% and 0.7% respectively in control subjects. Serum total cholesterol (5.1 v 4.5 mmol/l), low density lipoprotein cholesterol (3.2 v 2.6 mmol/l), non-esterified fatty acids (0.91 v 0.50 mmol/l), and triglycerides (0.94 v 0.76 mmol/l) were higher in diabetic children. Serum total cholesterol, triglycerides, and apolipoprotein (apo)B concentrations increased with worsening control, while serum high density lipoprotein cholesterol and apoA-I concentrations were unaltered. There were also positive correlations between glycated haemoglobin and total cholesterol, triglycerides, and apoB in diabetic children. Thus, abnormalities in circulating lipids are common in young subjects with IDDM but largely disappear if blood glucose concentrations are reasonably controlled.

An evaluation of multiple choice questionnaires for the assessment of knowledge in diabetic children and their families

The comparability of five multiple choice questionnaires was tested in 69 diabetic children and their parents. Analysis of variance showed that 68% of the variation in the scores was due to differences between individuals, with only 8% due to differences between questionnaires. A second study then compared results from diabetic children, their mothers and fathers, and some nurses and doctors, who each completed one questionnaire. Analysis of variance of this study showed that the mothers, fathers, and nurses scored about the same, but more than the children (p less than 0.05), whilst the scores of the doctors were not significantly different from any of the other groups.

Dietary variation in diabetics

The day to day variation in the energy and carbohydrate intake of 168 children with diabetes on Tyneside and Teesside was less than that of 405 non-diabetic children. It was, however, still considerable, the average range of carbohydrate intake over three days being 51 g. The variation in carbohydrate intake was not related to diabetic control nor to the families' knowledge of diabetes. Compliance with the dietary prescription deteriorated during the day. These findings support a qualitative approach to the dietary prescriptions for diabetics.

Hypothyroidism and growth failure in diabetes mellitus

The prevalence of thyroid disease in 134 children, adolescents, and young adults with diabetes mellitus beginning in childhood is described. Clustering of a family history of thyroid disease and the presence of thyrogastric antibodies in some patients supports the concept of familial autoimmunity. In 4 children a diagnosis of hypothyroidism had already been made, one of whom had shown marked faltering of growth. In a further 3 there was evidence of previously unrecognised subclinical hypothyroidism but the growth of 2 of them had been good. The findings of this study indicate that while subclinical hypothyroidism should be considered in a diabetic whose growth is faltering, it is rarely a cause of such growth failure.

A controlled trial of pyridoxine supplementation in children with febrile convulsions

A total of 107 children who had been hospitalized following a febrile convulsion were enrolled into the trial. By random allocation, 55 children were treated with pyridoxine hydrochloride (20 mgs twice daily) and the remaining 52 children were treated with a placebo until there had been either a further convulsion or a year had passed without recurrence. Eighty children were adequately followed up and of these, 17 had a recurrent febrile convulsion while receiving medication. Recurrences occurrences occurred in 7 of the 38 children receiving pyridoxine and in 10 of the 42 children receiving placebo (X2 = .346, p greater than 0.5). Initial tryptophan load tests had been abnormal in 34 children, and of these, recurrences occurred in 3 of the 17 who received pyridoxine and in 3 of the 17 who received placebo. It has yet to be shown that pyridoxine supplementation protects children from recurrent febrile convulsions.

Intra-uterine death resulting from placental metastases in adenocarcinoma of unknown primary

A thirty-five year old woman presented with bilateral neck, chest wall and back masses. She was 16 weeks pregnant. Lymph node excision revealed metastatic poorly differentiated adenocarcinoma of unknown primary. Abdominal ultrasound showed a mildly enlarged spleen and a 2-3 cm porta hepatis node. All other investigations were negative. The lymph node and cutaneous metastases progressed rapidly so it was decided to initiate systemic chemotherapy with a view to delivery at 28 weeks gestation by Caesarean section. Shortly after the second 3-weekly cycle of cisplatinum chemotherapy the patient suffered severe lower back and hip pain with MRI scan showing multiple bony metastases in the pelvic girdle. Ultrasound revealed the fetus to have been dead for at least 10 days. The products of conception were delivered following medical induction of labour. Two days later the patient suffered a cardiac arrest from which she could not be resuscitated. Placental histology revealed extensive metastases. With the exception of melanoma this has rarely been reported in solid adult malignancy. As a cause of fetal death, placental metastases are extremely rare.

Do education groups help diabetics and their parents?

The importance of education in the management of diabetes is recognised but has rarely been assessed in children. In a longitudinal controlled study we have examined the effect of a programme of education on the knowledge, diet, and concentration of glycated haemoglobin A1c in a group of diabetics. The programme took the form of two packages of education each consisting of four weekly meetings, in which small groups of parents and older children were led in a discussion of different aspects of diabetes. Only one of the 119 families who began the study failed to complete it. Family knowledge about diabetes improved as a result of the programme, although this was poorly retained in the fathers. A trend to improvement in several aspects of diet was noted but did not reach significance. A significant fall in glycated haemoglobin A1c was apparent seven months after the education in children aged 11 years and over. Those whose initial control was poor improved most. We conclude that such meetings should be considered as a useful adjunct to regular diabetic clinics.

HLA antigens and growth in diabetic children

HLA types in 121 diabetic children in Newcastle are examined in relation to their growth records. The children's height at the onset of diabetes was normal, but fell away during the course of the disease; there was low mean height velocity and failure of bone development to keep pace with chronological age. The total series shows the expected excess of HLA antigens B8, B15 and Cw3 and deficit of B7. Children with B8 are of smaller stature adjusted for bone age than those without the antigen, while children with B7 appear to do better. The results suggest that within the diabetic spectrum of genotypes the HLA antigens are relevant to growth and development.

How do childhood diagnoses of type 1 diabetes cluster in time?

Background

Previous studies have indicated that type 1 diabetes may have an infectious origin. The presence of temporal clustering—an irregular temporal distribution of cases—would provide additional evidence that occurrence may be linked with an agent that displays epidemicity. We tested for the presence and form of temporal clustering using population-based data from northeast England.

Materials and Methods

The study analysed data on children aged 0–14 years diagnosed with type 1 diabetes during the period 1990–2007 and resident in a defined geographical region of northeast England (Northumberland, Newcastle upon Tyne, and North Tyneside). Tests for temporal clustering by time of diagnosis were applied using a modified version of the Potthoff-Whittinghill method.

Results

The study analysed 468 cases of children diagnosed with type 1 diabetes. There was highly statistically significant evidence of temporal clustering over periods of a few months and over longer time intervals (p<0.001). The clustering within years did not show a consistent seasonal pattern.

Conclusions

The study adds to the growing body of literature that supports the involvement of infectious agents in the aetiology of type 1 diabetes in children. Specifically it suggests that the precipitating agent or agents involved might be an infection that occurs in “mini-epidemics”.

Children with diabetes mellitus: perception of their behavioural problems by parents and teachers

The behaviour of 127 children with diabetes mellitus aged 8-16 years was assessed by their parents and teachers using a well established screening device and compared to that of 51 non-diabetic children. Twenty five per cent of the diabetics were perceived by their parents to be disturbed compared to only 14% of the controls. The proportion perceived to be disturbed by their teachers was similar in the two groups but more diabetics than controls were perceived by both parents and teachers to be disturbed. No relationship was found between the extent of the behaviour problems recorded and the control of the diabetes, as measured by glycosylated haemoglobin, the child's age, the child's age at diagnosis or the duration of the diabetes. However, the children with the younger parents at diagnosis tended to be perceived by their parents as having more behaviour problems, as were the diabetics from families facing the most social problems. The families more knowledgeable about diabetes were less likely to have disturbed children.

Space-time clustering analyses of type 1 diabetes in children from north-east England: support for an infectious aetiology?

BACKGROUND

The aetiology of type 1 diabetes in children is uncertain. A number of recent studies have suggested an infectious aetiology. It has been postulated that an infectious agent may be involved. Support for this hypothesis may be provided by a finding of space-time clustering. The aims of this study were: (i) to determine whether there was space-time clustering in cases of childhood diabetes from north-east England; and to test for differences in space-time clustering: (ii) due to age at diagnosis; (iii) between the sexes and (iv) between levels of residential population density.

METHODS

We studied incidence of type 1 diabetes diagnosed in children aged 0-14 years and diagnosed during the period 1990-2007. All cases were resident in a defined geographical region of north-east England (Northumberland, Newcastle upon Tyne and North Tyneside). We applied a second-order procedure based on K-functions to test for global clustering. Locations were residential addresses at time of diagnosis. Tests were repeated using nearest neighbour thresholds to allow for variable population density, providing the primary result for each analysis. Differences between sexes and between levels of population density were assessed.

RESULTS

We analysed 457 cases of type 1 diabetes. Overall, there was marginally significant evidence of global space-time clustering (P = 0.089). There was statistically significant clustering amongst pairs of cases that contained at least one female (P = 0.017), but not amongst pairs of cases that contained at least one male (P = 0.190). Furthermore, there was significant clustering amongst pairs of cases that contained at least one from a more densely populated area (P = 0.044), but not amongst pairs of cases that contained at least one from a less densely populated area (P = 0.226).

CONCLUSION

Although the analyses have only found marginally significant evidence of global space-time clustering for cases of type 1 diabetes diagnosed in north-east England, there were two notable findings. First, there was evidence of clustering amongst females and secondly clustering was confined to cases from more densely populated areas. These findings are consistent with a possible aetiological involvement of an infectious agent.

Lipid levels in schoolchildren in north east England: effects of feeding and age

Serum total cholesterol, high-density lipoprotein (HDL) cholesterol, triglyceride, apolipoprotein (apo) A-I and apoB concentrations were estimated and low-density lipoprotein (LDL) cholesterol levels were calculated in 132 children aged 11.4-17.3 years. The effect of feeding was investigated by estimating postprandial values and also by studying the effects of a test meal. The distribution of all data was consistent with Gaussian apart from triglycerides which was log normal. Overall fasting values were [mean (standard deviation; SD)] cholesterol 4.5 (0.8) mmol/L, HDL cholesterol 1.5 (0.4) mmol/L, LDL cholesterol 2.6 (0.8) mmol/L, apoA-I 1.5 (0.3) g/L, apoB 1.0 (0.4) g/L and triglycerides 0.76 (0.38-1.51) mmol/L, the values for triglycerides being mean (95% confidence intervals). Girls had higher triglycerides than boys [0.82 (0.43-1.54) versus 0.70 (0.36-1.33)] and different effects of age on lipids were found, HDL cholesterol being negatively correlated with age in boys (r = -0.37; P < 0.001), but not in girls, and apoA-I being negatively correlated with age in boys (r = -0.31; P = 0.006), but positively correlated with age in girls (r = 0.32; P = 0.008). Triglycerides rose and HDL cholesterol fell following feeding and inconsistent effects were seen on apoA-I and apoB.

Hydroxykynurenine/hydroxyanthranilic acid ratios and febrile convulsions

Hydroxykynurenine/hydroxyanthranilic acid ratios were measured in children with febrile convulsions, afebrile fits, and fever, as well as in healthy controls. Increased ratios were found not only in the children who had fits but also in the children who were febrile and did not have fits. It is suggested that a raised hydroxykynurenine/hydroxyanthranilic acid ratio does not necessarily indicate vitamin B6 deficiency but may represent a nonspecific response of tryptophan metabolism to stress.