Predictors of participant retention in two chemoprevention feasibility trials

Retention of participants for intervention and follow-up activities is critical in cancer chemoprevention trials. Little has been published about retention patterns and predictors of retention in prevention studies. The Carotene and Retinol Efficacy Trial (CARET) provides an opportunity to study retention of volunteer participants in a large, long-term clinical trial. Two pilot studies were conducted in different populations to test the feasibility of critical strategies for the long-term study. Thirteen percent of the asbestos-exposed workers and 18% of the smokers became inactive during the pilot study. Of those remaining active, all but 2% of asbestos-exposed workers pilot study participants and 5% of smokers pilot study participants chose to participate in the full-scale efficacy trial. Five baseline predictors of inactivity for the asbestos-exposed participants emerged: being non-White, being a current smoker, having a history of high blood pressure at baseline, reporting two or more increases in symptoms during the placebo run-in, and having higher baseline levels of negative mental health measures (i.e. anxiety, depression, and fatigue). The only significant predictor of inactivity for smoker pilot participants was reporting symptoms during the placebo run-in. The most frequently reported reasons for becoming inactive during the pilot studies were general health issues and problems and symptoms that were seen as specific to the CARET vitamins. These findings suggest areas that could be tested to optimize retention in clinical trials.

Enantioselective induction of cyclophosphamide metabolism by phenytoin

The objective of this study was to investigate the effect of phenytoin (PHE) on cyclophosphamide (CP) disposition. CP was administered to 6 adult patients in a preparative regimen for bone marrow transplantation consisting of busulfan and CP. Three of the patients received PHE and the other 3 "control" patients received diazepam (DZP) as anti-epileptic prophylactic treatment. Plasma samples were collected at intervals up to 24 h after CP administration. The plasma concentrations of (R)- and (S)-CP and their respective N-dechloroethylated metabolites, (R)- and (S)-DCE-CP were simultaneously fitted using an enantiospecific 2-compartment pharmacokinetic (PK) model with Bayesian control estimation. DZP had no significant effect on the metabolism of CP and any of its PK parameters. PHE, however, increased significantly the formation of (S)-DCE-CP while having no effect on the formation of (R)-DCE-CP. These results suggest that different enzymes are responsible for the formation of (S)-DCE-CP from (S)-CP and (R)-DCE-CP from (R)-CP. Additionally, assuming that PHE does not affect the passive renal elimination of (R)- and (S)-CP, this analysis suggests that the clearance of both (R)- and (S)-CP to 4-hydroxy-CP (the activation pathway) is increased by PHE.

Small noncleaved, non-Burkitt's (Burkit-Like) lymphoma: cytogenetics predict outcome and reflect clinical presentation

PURPOSE

To correlate cytogenetic abnormalities with clinical presentation and outcome in Burkitt-like, small noncleaved non-Burkitt's lymphoma (SNC-NB).

PATIENTS AND METHODS

Thirty-nine patients with SNC-NB lymphoma and a clonal karyotype were evaluated between January 1989 and January 1996. All were from British Columbia, Canada, underwent uniform clinical staging, and were treated on investigational protocols by a small group of clinicians.

RESULTS

Three groups of patients were identified by clonal karyotype on cytogenetic analysis: (1) those with a c-myc translocation (n = 11); (2) those with dual translocation of c-myc and bcl-2 (n = 13); and (3) those with other cytogenetic abnormalities (n = 15). The c-myc group was younger, presented with earlier stage de nova disease, and had a better clinical prognostic factor profile. The dual-translocation and other groups were older and presented in advanced stage with poorer prognostic features, and a larger proportion of the dual-translocation group patients had transformed from previously diagnosed follicular lymphoma. The median overall survival (OS) time for all patients was 5 months. The median OS time for the dual-translocation group was only 2.5 months, as compared with 7 months and 8 months for the c-myc and other group, respectively (P < .001). There were no survivors beyond 7 months among the dual-translocation group, as opposed to 32% and 25% 2-year OS rates in the c-myc and other group.

CONCLUSION

SNC-NB lymphoma is a clinically and cytogenetically heterogenous disease. Dual translocation of c-myc and bcl-2 is characterized by a rapid clinical course and extremely poor outcome. This latter entity may represent the most clinically aggressive lymphoma thus far characterized and warrants intensive investigational treatment where feasible.

Mother-to-child transmission of human T-cell lymphotropic virus type I associated with prolonged breast-feeding

OBJECTIVES

We assessed the risk of transmitting human T-cell lymphotropic virus type I (HTLV-I) through breast-feeding.

STUDY DESIGN/METHODS

To assess the risk of mother-to-child transmission of HTLV-I, 212 HTLV-I-seropositive women and 145 HTLV-I-seronegative women were enrolled in a prospective cohort study conducted in Kingston, Jamaica. Their offspring were examined at regular intervals, and HTLV-I serostatus was determined at each visit.

RESULTS

Twenty-eight of the 181 children with at least one postnatal visit born to HTLV-I-seropositive women (and none of the children born to HTLV-I-seronegative women) were persistently seropositive and were considered HTLV-I infected (Kaplan-Meier estimated cumulative incidence, 18%; 95% CI, 12%-24%). Among children observed for at least 24 months, 19 (32%) of 60 children breast fed for 12 months or longer were HTLV-I seropositive, compared with only 8 (9%) of 86 children breast-fed for less than 12 months (relative risk, 3.4; 95% CI, 1.7-6.9). Compared with children weaned at younger ages, transmission of HTLV-I was associated with continued breast-feeding of children who were 12 to 18 months of age (relative hazard, 6.4; 95% CI, 2.1-180.2) and older than 18 months (relative hazard, 18.1; 95% CI, 1.4-29.5). Transmission was also associated with higher maternal antibody titer (a possible marker of virus load), prolonged duration of ruptured membranes during childbirth, and lower maternal income.

CONCLUSIONS

These results suggest that limiting the duration of breast-feeding to less than 12 months for children born to HTLV-I-seropositive mothers may significantly reduce mother-to-child transmission of HTLV-I.

Dietary guar gum improves insulin sensitivity in streptozotocin-induced diabetic rats

Although dietary recommendations for diabetics stress the need for increased carbohydrate and dietary fiber, the effectiveness of dietary fiber in improving insulin sensitivity remains controversial. The aim of this study was to compare the effects of a soluble fiber (guar gum) and an insoluble fiber (wheat bran) on insulin sensitivity in streptozotocin-induced (STZ) diabetic rats. Consequently, the rats were divided into two groups and one half were rendered diabetic with streptozotocin. The STZ diabetic and nondiabetic rats were further randomized and fed a diet containing dietary fiber (7 g/100 g diet) from either guar gum or wheat bran. The hyperinsulinemic clamp technique, combined with infusion of the glucose analog, 2-deoxyglucose (2DG), was utilized to examine insulin sensitivity. Bran-fed STZ diabetic rats were significantly (P < 0.001) hyperglycemic, which was ameliorated by guar gum. Insulin-mediated glucose disposal was increased by the guar diet compared with the bran diet in both the STZ diabetic rats [17.7 +/- 2.2 vs. 11.8 +/- 2.4 mL/(kg x min), P < 0.05] and the nondiabetic rats [20.5 +/- 2.8 vs. 15.5 +/- 1.5 mL/(kg x min), P < 0.05]. The accumulation of 2DG in peripheral muscles reflected the changes in insulin sensitivity with a trend for increased 2DG uptake in the majority of analyzed tissues in rats fed the guar diet, both nondiabetic and STZ diabetic, compared with the bran-fed rats. Accompanying these alterations in insulin sensitivity, guar gum suppressed food intake in the hyperphagic diabetic rats by 20% (P < 0.001). The present results demonstrate the effectiveness of guar gum in improving insulin sensitivity in STZ diabetic rats and suggest that reduced food intake may be an important mechanism of action of guar in hyperphagic diabetic rats.

The effect of inhibiting fatty acid oxidation on basal glucose metabolism in Psammomys obesus

We administered etomoxir (an inhibitor of fatty acid oxidation) for five days at a dose of 50 mg/kg/day to three groups of Psammomys obesus. Group A were normoglycemic and normoinsulinemic, group B were normoglycemic and hyperinsulinemic, and group C were hyperglycemic and hyperinsulinemic. When compared with group A, the hyperglycemic/hyperinsulinemic rats of group C had elevated hepatic glucose production (HPG) and elevated glucose uptake (Rg) in all tissues measured reaching statistical significance in white gastrocnemius, soleus and diaphragm. Five days of etomoxir treatment reduced the plasma glucose levels of group C. Etomoxir treatment reduced HGP and although the change was not significant, it was supported by significant reductions of Rg in several tissues including diaphragm, heart, small intestine, brain and white adipose tissue. Five days of etomoxir treatment also reduced the plasma insulin levels in group B and group C, when compared to the levels before treatment. These results demonstrate that inhibition of fatty acid oxidation significantly reduced hyperglycemia, hyperinsulinemia and Rg in some tissues in group C animals suggesting that elevated levels of fatty acid oxidation and increased glucose turnover may be associated with development of NIDDM in Psammomys obesus.

Computer simulation of transposable element evolution: random template and strict master models

It has been proposed that the most extensively studied mammalian retrotransposons replicate by some form of a master template model. This conclusion has been drawn largely from DNA sequence analysis and is based on phylogenetic tree topology, the presence and ordering of shared variants, the degree of divergence between elements within a subfamily, and the shape of the distribution of pairwise differences between elements. To investigate how robust these parameters are as predictors of the model of transposition, computer simulations of the two most extreme transposition models, the Random Template Model and the Strict Master Model, were carried out. A prototype of a computer simulator for studying retrotransposition is presented. The simulator is a versatile digital workbench that maintains DNA sequence data and allows manipulation of a range of factors including reverse transcriptase and in situ mutation rates, transposition template, and transposition rate. All parameters previously used as predictors of the model of transposition were markedly different for the two extreme models when evaluated using large sample sizes of sequences from experiments simulating up to 15 million years of evolution.

Multi-organ dysfunction associated with high-dose carboplatin therapy prior to autologous transplantation

The specific contribution of high-dose carboplatin to regimen-related toxicity after autologous transplantation has been difficult to determine, particularly in patients receiving cyclophosphamide or ifosfamide. We report five cases of severe multi-system failure in patients receiving high-dose carboplatin in addition to other cytotoxics prior to autologous transplantation. Two of these patients did not receive ifosfamide or cyclophosphamide as part of their chemotherapy. The clinical picture consisted of early onset acute renal failure, arrhythmias and/or myocardial hypokinesia, mental obtundation and other neurological deficits and, in two patients, an acute myopathy. In the two patients in whom serum platinum was measured, levels were very high at the time of marrow infusion. All patients had received prior cisplatin therapy but showed either normal or only modestly impaired creatinine clearance before the transplant. These observations are consistent with a specific clinical syndrome associated with carboplatin toxicity and suggest that creatinine clearance may be inadequate as an indicator of potential renal failure when high-dose carboplatin is used.

The molecular biology of temperature-dependent sex determination

Many reptiles do not have heteromorphic sex chromosomes and for these species sex is determined during embryogenesis by the temperature of egg incubation rather than at conception. The phenomenon of temperature-dependent sex determination (TSD) was discovered almost thirty years ago, but few advances have been made towards the elucidation of its mechanism. In the past few years substantial progress has been made in the understanding of the molecular basis of XY chromosomal (genetic) sex determination (GSD) through the discovery of SRY. It is now possible to start comparing TSD with GSD. TSD is found in some evolutionarily ancient vertebrates and has been postulated to be the ancestral process from which GSD has evolved. If this is true then the two mechanisms may share a common molecular basis. This paper details the current knowledge of TSD, our progress on the investigation of the involvement of SRY-type proteins, and finally presents some of the problems that need to be resolved to gain an understanding of the molecular basis of TSD.

Basal glucose turnover in Psammomys obesus. An animal model of type 2 (non-insulin-dependent) diabetes mellitus

The aim of this study was to examine whole-body glucose turnover and glucose uptake into individual tissues in Psammomys obesus. The animals were classified according to the level of circulating glucose and insulin in the fed state: group A was normoglycaemic and normoinsulinaemic (glucose < 8.0 mmol/l), insulin < 150 mU/l), group B was normoglycaemic and hyperinsulinaemic (glucose < 8.0 mmol/l, insulin > or = 150 mU/l), and group C was hyperglycaemic and hyperinsulinaemic (glucose > or = 8.0 mmol/l, insulin 150 mU/l). The animals were deprived of food for 6 h, after which they were anaesthetized and cannulated, using the jugular vein for infusions and the carotid artery for blood sampling. Whole-body glucose turnover was measured using a primed-continuous infusion of 6-[3H]-glucose and saline to quantitatively assess hepatic glucose production (HGP), glucose disposal (Rd), and the metabolic clearance rate of glucose (MCR). Following the 2-h infusion period, the glucose metabolic index (Rg') of individual tissues was measured using a fixed-dose bolus of 2-deoxy-[14C] glucose. Under the steady-state conditions of the experiment, HGP was assumed to be equal to Rd, and both variables were found to be significantly correlated to the fasting glucose concentration (r=0.534, P<0.05, n=19). On the other hand, MCR was found to be inversely correlated to the fasting plasma glucose concentration (r=0.670 P < 0.01, n=19). When the animals were divided into three groups as described above, HGP in group C animals was significantly elevated compared with group A (20.8 +/- 2.6 vs 12.7 +/- 0.6 mg.kg-1.min-1; P < 0.05), and MCR showed a tendency to be lower in group C than group A, although the difference was not statistically significant. HGP and MCR were not significantly different between groups A and B. Measurement of the glucose metabolic index in individual tissues showed that group C animals had significantly higher Rg' values in muscles and adipose tissues compared with those in group A (P < 0.05). In addition, Rg' in group B white gastrocnemius and soleus were significantly higher than in group A despite similar rates of HGP and levels of glycaemia. These findings suggest that an early increase in skeletal muscle glucose uptake and hyperinsulinaemia can be demonstrated in group B Psammomysobesus before significant hyperglycaemia.

The effect of restricting energy intake on diabetes in Psammomys obesus

The aim of this paper was to determine whether restricting energy intake would reduce the elevated levels of glucose, insulin, cholesterol and triglyceride in diabetic Psammomys obesus (sand rat). Between 11 and 12 weeks of age Psammomys obesus were divided into three groups based on blood glucose and plasma insulin levels in the fed ad libitum state; group 1 was normoglycemic (4.4 +/- 0.3 mM) and normoinsulinemic (0.46 +/- 0.04 ng/ml), group 2 was normoglycemic (5.0 +/- 0.3 mM) and hyperinsulinemic (3.58 +/- 0.62 ng/ml) and group 3 was hyperglycemic (11.2 +/- 1.2 mM) and hyperinsulinemic (6.23 +/- 0.73 ng/ml). Energy intake was restricted to 67% of normal for 2 weeks before ad libitum feeding was resumed for a further 2 weeks. Animals in group 3 developed the most abnormalities when compared to group 1 including increased levels of food intake (16.3 +/- 0.5 vs 14.2 +/- 0.5 g/day, P < 0.05), body weight (192 +/- 5 vs 162 +/- 4 g, P < 0.05), triglycerides (1.5 +/- 0.2 vs 0.96 +/- 0.08 mM, P < 0.05), and cholesterol (2.8 +/- 0.2 vs 2.1 +/- 0.1 mM, P < 0.05). In group 3, food restriction was effective in reducing glucose levels (but not insulin) both during and following the restriction period respectively (11.2 +/- 1.2 vs 4.6 +/- 0.5, and 5.9 +/- 1.3, mM, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

A cross-sectional and short-term longitudinal characterisation of NIDDM in Psammomys obesus

The present study was undertaken to examine the cross-sectional and short-term longitudinal changes in glucose and insulin concentrations as well as measure the enzymatic activity of PEPCK and glycogen synthase in our Psammomys obesus colony. In the cross-sectional study, blood samples were taken from one group of animals at 19 weeks of age (n = 37) in the fed state and following a 4-h fast. In a separate group of 19-week-old animals (n = 69), samples were taken 1 h following an OGTT (1 g/kg body weight) in Psammomys subjected to a 16-h fast. In the longitudinal study, blood samples were taken from one group of animals in the fed state at 7, 11, 15 and 19 weeks of age. All of the cross-sectional data have described the classic inverted U-shaped curve (Starling's curve of the pancreas) in the relationship between glucose and insulin levels. This trend was also reflected by Psammomys subjected to the OGTT; a mild impairment in glucose tolerance was associated with an increase in the insulin response and a further impairment in glucose tolerance was associated with a reduction in the insulin response. Similar results were obtained following a 4-h fast. The short-term longitudinal glucose and insulin data revealed that of the 37 animals examined over the 12-week period, 16 progressed along the inverted U-shaped curve described by the cross-sectional data. Of the other animals, 8 remained unchanged, 7 were unclassifiable and 6 hyperglycaemic Psammomys developed normoglycaemia at the expense of elevated insulin levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Autologous transplants for chronic myelogenous leukaemia: results from eight transplant groups

Chronic myelogenous leukaemia (CML) can be cured by donor marrow transplant. Unfortunately, suitably HLA-matched related or unrelated donors are not available for the majority of patients. Transplant of stem cells derived from a patient's own marrow or peripheral blood (autologous transplant) avoids the need for an HLA-matched donor, is associated with a less complicated and shorter hospital course than donor transplantation, and has been successful in the treatment of other haematological malignancies. We report results of autologous transplants in 200 patients with CML at eight marrow transplant centres over seven years. This is the first multicentre analysis of autologous transplants for CML and reports on the largest number of patients studied to date. We show that autologous transplants provide a plateau in the survival curve not observed in conventional treatments. Autologous transplants are associated with a high engraftment rate, low mortality, and prompt return of both younger and older patients to normal activity levels. Our results suggest that autologous transplants provide an alternative to conventional treatment in the care of patients not eligible for donor transplant.

The prevention of accelerated cardiac allograft rejection in sensitized recipients after treatment with brequinar sodium

Brequinar sodium (BQR) is a novel immunosuppressive agent that is highly effective in preventing B lymphocyte-mediated antibody production. We have examined the effects of BQR treatment in sensitized recipients on graft survival, donor-specific antibody responses (IgM and IgG), and the appearance of immunopathological lesions present in the grafts. LEW rat recipients were sensitized with single ACI skin graft on day 7 and received heterotopic ACI cardiac grafts on day 0. The recipients rejected the cardiac grafts in an accelerated fashion at day 2.5 post-transplantation, compared to day 7.0 in unsensitized recipients. The animals were treated with low (3 mg/kg/day) or high (12 mg/kg/3x weekly) doses of BQR during skin graft sensitization and/or after challenge with ACI heart allografts. All groups treated with BQR showed significant prolongation of graft survival in the sensitized recipients. The best survival was observed following high-dose BQR therapy during both sensitization and effector phases (median survival time = 40.0 days, P << 0.001). Daily treatment with BQR (3 mg/kg/day) prevented IgM (but not IgG) antibody responses. Treatment with higher doses of BQR (12 mg/kg/3x weekly) before and after skin graft sensitization was effective in preventing both IgM and IgG production. In general, BQR treatment resulted in effective suppression of anti-donor antibody responses, stable graft function, and a reduction in the severity of the acute vascular lesions in the graft. The effectiveness of BQR in preventing accelerated graft rejection when used at 12 mg/kg/3x weekly was comparable to that seen with treatment of sensitized animals with CsA at 15 mg/kg/day for 30 days. Daily treatment with cyclophosphamide at 5 or 15 mg/kg/day was ineffective for preventing graft rejection in sensitized recipients. These results indicated that BQR may provide an important addition to treatment protocols designed to prevent transplantation rejection in presensitized patients. BQR has the ability to significantly inhibit host cellular and humoral immune responses to the donor graft and this facet of the immunosuppressive activity of the drug may be responsible for preventing this aggressive form of rejection.

The biology of normal and neoplastic stem cells in CML

Chronic myeloid leukemia (CML) has long served as a prototype malignancy for basic as well as clinical studies aimed at developing curative cancer treatment protocols. Well established features of chronic phase CML are its origin in a pluripotent stem cell, a now well defined molecular genetic basis involving the creation of a BCR-ABL fusion gene and evidence of resultant abnormalities in the mechanisms that normally control primitive hemopoietic cell proliferation. We have recently shown how the long-term marrow culture system can be adapted to quantitate and characterize a very primitive cell type in normal blood and marrow samples, as well as their normal and leukemic counterparts in patients with CML. This system has also been used to dissect mechanisms of normal progenitor regulation and to identify specific anomalies affecting leukemic (CML) progenitors. Our studies show that cells detected by their ability to initiate long-term cultures (LTC) of leukemic cells (i.e., CML LTC-initiating cells or LTC-IC) are differently distributed between marrow and blood by comparison to LTC-IC in normal individuals and, although functionally similar in terms of the number and differentiation types of clonogenic cells they produce, CML LTC-IC exhibit defective self-maintenance. Phenotypically these primitive leukemic cells are heterogeneous; the majority display features of activated/proliferating cells but a significant proportion do not. We have also documented heterogeneity in primitive CML cell responses to two factors that specifically and reversibly arrest the cycling of primitive normal hemopoietic cells; i.e., TGF-beta and MIP-1 alpha, to which CML cells are normally responsive and abnormally unresponsive, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)