Modulation of drug resistance mediated by loss of mismatch repair by the DNA polymerase inhibitor aphidicolin

Loss of expression of mismatch repair (MMR) proteins leads to resistance of tumor cells to a variety of DNA-damaging agents, including bifunctional alkylating and monofunctional methylating agents such as cis-diaminedichloroplatinum II (CDDP) and N'-methyl-N-nitrosourea (MNU). It has been suggested that coupling to cell death does not occur in the absence of MMR, but instead, DNA lesions are bypassed during replication, giving a drug-tolerant phenotype. In the present study, we have used aphidicolin (Ap), an inhibitor of DNA polymerases, to study the role of replicative bypass in drug resistance mediated by loss of MMR. We have examined the survival of matched ovarian carcinoma cell lines with known MMR status after sequential treatment with CDDP or MNU and Ap. We show that Ap increases the sensitivity of MMR-deficient cell lines to CDDP and MNU to a greater extent than their MMR-proficient counterparts. Furthermore, loss of MMR correlates with loss of CDDP-induced G2 arrest, but this is partially restored after Ap treatment. These data support Ap sensitizing drug-resistant cancer cells that have lost MMR to CDDP and MNU and suggest that the potential use of Ap as a modulator of drug resistance should be targeted to MMR-defective tumors.

Oxidative stress induced in pathologies: the role of antioxidants

Exposure to oxidant molecules issued from the environment (pollution, radiation), nutrition, or pathologies can generate reactive oxygen species (ROS for example, H2O2, O2-, OH). These free radicals can alter DNA, proteins and/or membrane phospholipids. Depletion of intracellular antioxidants in acute oxidative stress or in various diseases increases intracellular ROS accumulation. This in turn is responsible for several chronic pathologies including cancer, neurodegenerative or cardiovascular pathologies. Thus, to prevent against cellular damages associated with oxidative stress it is important to balance the ratio of antioxidants to oxidants by supplementation or by cell induction of antioxidants.

Optimizing force and velocity: mandible muscle fibre attachments in ants

To be able to perform swift and powerful movements, ant mandible closer muscles are composed of two subpopulations of muscle fibres: fast fibres for rapid actions and slow fibres for forceful biting. All these fibres attach to a sturdy and complex apodeme which conveys force into the mandible base. Fast muscle fibres attach directly to the apodeme. Slow fibres may attach directly or insert at individual thin filament processes of the apodeme which vary in length. Comparisons of different ant species suggest two basic principles underlying the design of mandible muscles. (1) Ants specialized for fast mandible movements generally feature long heads which contain long fast muscle fibres that attach to the apodeme at small angles. Their muscles comprise only a few filament-attached fibres and they maximize speed of action at the expense of force output. (2) Ants performing particularly forceful mandible movements, such as seed cracking, rely on many short parallel muscle fibres contained within a broad head capsule. Their slower muscles incorporate a large proportion of filament-attached fibres. Two simple models explain how the attachment angles are optimized with respect to force and velocity output and how filament-attached fibres help to generate the largest power output from the available head capsule volume.

Primary bacterial colonization of implant surfaces

The purpose of this study was to assess the effects of modifying titanium surfaces, in terms of wettability, roughness, and mode of sterilization, on the ability of the oral bacterium Streptococcus sanguis to colonize. An in vitro model system was developed. All surfaces were colonized by the bacteria, but to significantly different levels. Titanium samples that exhibited rough or hydrophobic (low wettability) surfaces, along with all autoclaved surfaces, were preferentially colonized (P < .01). Titanium surfaces that had been repeatedly autoclaved were colonized with the levels of bacteria 3 to 4 orders of magnitude higher than other modes of sterilization. This may have implications relative to the commonly used method of autoclaving titanium implants, which may ultimately enhance bacterial biofilm formation on these surfaces.

The economic consequences of smoking in Ontario

Smoking causes health and social problems such as sickness, death, fire, injury, pain and suffering. This paper provides an estimate of the economic burden imposed by the adverse health and social consequences of smoking in Ontario in 1992. The cost-of-illness method, in particular, the human-capital approach is used to estimate the prevalence-based economic costs of smoking. The direct and indirect components of smoking-related costs are estimated and the total cost in Ontario is US$2.91 billion. Associated with these economic costs are health-related harms: 69,318 hospital separations; 1,007,647 days stay in hospitals; 11,648 deaths resulting in more than 171,443 person-years lost.

Fatal bleomycin pulmonary toxicity in the west of Scotland 1991-95: a review of patients with germ cell tumours

We conducted a retrospective review of fatal bleomycin pulmonary toxicity in patients treated for germ cell tumours during 1991-95 at the Beatson Oncology Centre, Glasgow. Case notes of patients treated with bleomycin were reviewed with respect to cumulative bleomycin dose, renal impairment, exposure to supplemental oxygen, thoracic radiotherapy and age. A total of 194 patients underwent chemotherapy, of whom 180 received bleomycin-containing regimens. Five fatal cases of pulmonary toxicity were identified, an incidence of 2.8%. These cases were older than the remaining patients (P < 0.001), with a median age at diagnosis of 55 vs 33 years. The incidence of fatal pulmonary toxicity increased with each decade of life above age 30. Renal function also differed between the two groups, with the worst glomerular filtration rate recorded at the time of bleomycin administration for each patient, lower in the fatal group, median 69 vs 107 ml min(-1) (P < 0.001). There was no difference with respect to cumulative bleomycin dose or exposure to supplemental oxygen. For patients aged over 40 years, especially those with renal function in the lower range of normal, the risk of developing fatal toxicity may exceed 10%. The benefits of bleomycin could be questioned for this age group.

Early closure of a randomized trial: surgery and postoperative radiotherapy versus radiotherapy in the management of intra-oral tumours

Tumours of the oral cavity/oropharynx occur relatively infrequently in the UK. The management of such lesions, especially the squamous cell carcinomas, is still a little controversial. Some centres advocate radiotherapy while others adopt surgery and radiotherapy. In an attempt to resolve the question of which approach gives the better results, a multicentre randomized trial was established to compare surgery plus postoperative radiotherapy with radical radiotherapy alone. It was anticipated that 350 patients would be required to give a statistically significant result, but, after 35 patients had been entered, the trial was closed prematurely with a marked difference in overall survival in favour of the combination arm (P = 0.0006). At this analysis, carried out 23 months after trial closure, the survival difference between the two arms remains statistically significant for all causes of mortality (P = 0.001; relative death rate = 0.24; 95% CI 0.10-0.59).

Chronic diarrhoea among HIV-infected adult patients in Nairobi, Kenya

OBJECTIVES

Chronic diarrhoea and wasting are well recognized features of AIDS in Africa. However, because of resource constraints few comprehensive aetiological studies have been conducted in sub-Saharan Africa which have included a broad range of microbiological investigations. We undertook a prospective cross-sectional study of adult patients admitted to a government hospital in Nairobi, Kenya, to determine possible bacterial, mycobacterial, parasitic and viral causes of diarrhoea; to consider which may be treatable; and to relate microbiological findings to clinical outcome.

METHODS

Stool specimens from 75 consecutive HIV-seropositive patients with chronic diarrhoea admitted to a Nairobi hospital were subjected to microbiological investigation and results were compared with clinical findings and outcome. Stool samples were cultured for bacteria and mycobacteria and underwent light and electron microscopy; lawns of Escherichia coli were probed for pathogenic types and aliquots were tested for the presence of Clostridium difficile cytotoxin. Blood cultures for mycobacteria and other bacterial pathogens were performed as clinically indicated.

RESULTS

Thirty-nine (52%) patients yielded putative pathogens, the most common being Cryptosporidium sp. (17%), Salmonella typhimurium (13%), and Mycobacterium tuberculosis (13%). Of 41 patients investigated for pathogenic Escherichia coli, enteroaggregative E. coli and diffusely adherent E. coli were each found in four patients. Thirty-one (41%) patients died. Detection of cryptosporidium cysts was the single most significant predictor of death (X2 = 5.2, P<0.05). Many patients did not improve (21; 28%) or self-discharged whilst still sick (5; 7%) but five (7%) were diagnosed ante mortem with tuberculosis and treated and a further 13 (17%) showed improvement by time of discharge.

CONCLUSIONS

HIV-infected patients with chronic diarrhoea in Nairobi have a poor outcome overall, and even with extensive investigation a putative pathogen was identified in only just over half the patients. The most important step is to exclude tuberculosis; and the most useful investigation appears to be Ziehl-Neelsen staining. Other potentially treatable gram-negative bacterial pathogens, S. typhimurium, Shigella sp. and adherent E. coli were, however, common but require culture facilities which are not widely accessible for definitive identification. Further studies focussing on simple ways to identify sub-groups of patients with treatable infections are warranted.

Randomized multicentre trial of filgrastim as an adjunct to combination chemotherapy for Hodgkin's disease. West of Scotland Lymphoma Group

This study was intended to ascertain whether the adjunctive administration of filgrastim (r metHuG-CSF, Amgen) would influence the dose intensity of chemotherapy or the morbidity of myelosuppression in patients receiving MOPP or MOPP/EVAP hybrid chemotherapy for Hodgkin's disease. In a prospective randomized trial, two regimens for the treatment of Hodgkin's disease were compared. The substudy described here randomized patients receiving either regimen to receive filgrastim on the days when chemotherapy was not administered. During chemotherapy, parameters of myelosuppression were documented, including dose delays, the severity and duration of neutrophil and platelet nadirs, infective episodes, and resulting hospital admissions. In the MOPP arm, 13/25 eligible patients, and, in the MOPP/EVAP arm, 12/22 eligible patients, received filgrastim. The use of filgrastim made no statistically significant difference to the administered dose intensity for either MOPP (P = 0.57, 95% confidence interval (CI) 15-point increase to 8-point reduction) or MOPP/EVAP (P = 0.53; 95% CI 7-point increase to 11-point reduction). In patients receiving MOPP, filgrastim reduced the median duration of leucopenia (P = 0.007) and the severity of the white blood cell nadir (P = 0.036); however, no statistically significant effect (at the 5% level) was seen in platelet or haemoglobin nadirs, the number of days of in-patient hospitalization, the number of admissions for infective complications, the incidence, grade or duration of infections, or the incidence of febrile neutropenia. In patients receiving MOPP/EVAP, filgrastim had no significant effect on the duration or depth of leucopenia but was associated with a reduction in the median haemoglobin (P = 0.002) and platelet nadirs (P = 0.015). No effect on the above listed sequelae of myelosuppression was influenced by the administration of filgrastim. This study, although small, suggests that the routine use of filgrastim, aimed at influencing the administered dose intensity of conventional dose chemotherapy in Hodgkin's disease, is not warranted.

Bolus/infusional 5-fluorouracil and folinic acid. A report on two prospective, consecutive phase II studies with 5-fluorouracil dose escalation

We have used a relatively new trial methodology, the group sequential design, to prospectively evaluate two dose levels of bolus/infusional 5-fluorouracil (5-FU) and folinic acid in 192 consecutive-patients with advanced colorectal carcinoma. On day 1, all patients received 200 mg m(-2) of folinic acid infusion over 2 h. Cohort A (n = 102 patients) received 500 mg m(-2) 5-FU by i.v. 15-min infusion followed by an infusion of 500 mg m(-2) 5-FU over 22 h. Treatment was repeated on day 2 and further cycles given 2-weekly. After sequential analysis excluded a response rate of over 40%, cohort B (n = 90 patients) received an increased dose of 600 mg m(-2) 5-FU bolus and infusion. Patients had received no prior 5-FU therapy and the two cohorts had similar demographic features. In 179 evaluable patients, the overall response rate was 18% (95% CI 12-24%) with CR of 6% and PR of 12%, with no difference between the two cohorts. Overall median survival was 34 weeks (95% CI 30-39) with no significant difference between cohorts (median survival 32 and 37 weeks in cohort A and B respectively; P = 0.27). On multivariate analysis, poor performance status, elevated initial WBC and alkaline phosphatase and low serum albumin were associated with reduced survival (P < 0.05), and initial raised WBC showed an association with reduced likelihood of response (P = 0.002). Overall toxicity was low with CTC grade 3 mucositis, diarrhoea, nausea or vomiting in < or = 6% of patients and no treatment-related deaths. Significant (grade 3 or above) leucopenia was more common in cohort B than in cohort A (9% and 1% respectively); there were more dose reductions, and the median administered dose intensity was lower in cohort B than in cohort A (89% and 97% respectively; P = 0.006). In this group of relatively unselected patients, we have confirmed a relatively low objective response rate and median survival of 7.8 months with this regimen. There was no significant difference in outcome between the two dose levels but the higher dose of 5-FU was associated with more dose reductions and greater toxicity.

The economic costs of alcohol abuse in Ontario

The abuse of alcohol causes health and social problems, such as sickness, death, injury, pain, suffering and crime. These harms impose an economic burden on society. Resources are used or foregone as a consequence of alcohol abuse. This article provides an estimate of the economic cost of alcohol abuse in Ontario in 1992. It uses the cost-of-illness method, in particular, the human-capital approach to estimate the prevalence-based economic costs of alcohol abuse. This methodology is consistent with international guidelines formulated at the 1994 International Symposium on Economic and Social Costs of Substance Abuse. The direct and indirect economic costs of alcohol abuse are identified and estimated. The total economic cost of alcohol abuse, from a societal perspective, is estimated to be US$2261.10 million in Ontario in 1992.

Molecular changes in Entamoeba histolytica in response to bacteria

Entamoeba histolytica, the protozoan parasite, is the causative agent of amoebiasis. The degree of virulence, as inferred from invasiveness, of potentially pathogenic strains may be regulated by both host and parasite factors that determine the gut environment. One such factor that plays an important role is the bacterial flora in the gut. Previous studies have clearly shown that bacterial flora is an important determinant of virulence in E. histolytica. However, the exact nature of changes induced in E. histolytica in response to bacteria and their role in virulence is not clear. In this study the levels of a number of molecules potentially important in virulence mechanisms were determined in E. histolytica cells grown with and without normal human bacterial flora, using enzyme-linked immunosorbent assay. Significant changes were observed only after the E. histolytica cells had been adapted to grow with bacterial flora for a number of generations, and not in short term culture.

The economic costs of illicit drug use in Ontario, 1992

The use of illicit drugs causes health and social problems which imply economic costs to society. This paper uses the cost-of-illness method, in particular, the human-capital approach to estimate the prevalence-based economic costs of illicit drug use in Ontario in 1992. This methodology is consistent with international guidelines formulated at the 1994 International Symposium on Economic and Social Costs of Substance Abuse. The economic cost of illicit drug use is estimated at $489.29 million (Canadian dollars) in 1992. Associated with these costs are health-related harms: 211 deaths, half of which occur before the age of 35; and 20 690 days stay in public hospitals.

Interstitial iridium-192 implantation combined with external radiotherapy in anal cancer: ten years experience

PURPOSE

To report our experience in the use of interstitial iridium-192 implantation combined with external radiotherapy in anal cancer.

METHODS AND MATERIALS

From 1984 to 1994, 79 patients with anal cancer were treated with radical intent using radiotherapy (plus chemotherapy) at Beatson Oncology Centre, Glasgow, Scotland. The mean and median age at presentation were 68 and 70 years, respectively (range 34-85) with a male-to-female ratio of 0.39. The histologic distribution was as follows: 48 squamous, 16 basaloid, 14 adenocarcinoma, and 1 basal cell carcinoma. The T stages were: 8 T1, 40 T2, 26 T3, and 5 T4 lesions. Twelve (15%) patients had nodal involvement at presentation. All patients underwent interstitial implantation using iridium-192 as part of the initial treatment. Seventy-six patients were treated with external radiotherapy followed by implant with a mean delay of 37 days after the end of radiotherapy. Twelve patients also received chemotherapy with 5-fluorouracil and mitomycin-C concurrently with external radiotherapy. Follow-up ranged from 6 to 123 months, with a median of 37 months.

RESULTS

Seventy-nine patients were analyzed to assess local control, survival, and complications. A complete response rate of 91% (72 of 79) was achieved after planned radiation treatment. At the end of external radiotherapy, 29% (22 of 76) had achieved complete response, 58% (7 of 12) with chemotherapy and 23% (15 of 64) without it. Local control was achieved in 62 of 79 (78%) patients and 8 of 17 (47%) local failures were salvaged by abdominoperineal resection. Five patients developed inguinal node failure; four of these were salvaged. Overall, 10% of all patients developed distant metastasis as the first site of failure and 25% failed at any site after salvage therapy. Time to unsalvageable relapse was significantly different on comparing T stage (p = 0.005) and histology (p = 0.029) of tumor. Major complications requiring surgical intervention were seen in six (7.5%) patients. Anal function preservation with local control was possible in 56 of 79 (71%) patients.

CONCLUSION

We report excellent results with radiotherapy in T1 and T2 lesions. The role of chemoradiotherapy as radical treatment of anal cancer should be defined in the context of locally advanced tumors.

Health-related quality of life after knee replacement

A cross-sectional, community-based survey of a random sample of 1750 of 242,311 Medicare recipients was performed. The patients were at least sixty-five years old and had had a primary or revision knee replacement (either unilaterally or bilaterally) between 1985 and 1989. Three samples were surveyed separately: a national sample (to reflect the United States as a whole) and samples from Indiana and the western part of Pennsylvania (sites chosen for convenience to assess the validity of the findings for the national sample on a regional level). Each sample was stratified by race, age, residence (urban or rural), and the year of the procedure. Valid and reliable questionnaires were used to elicit the participants' assessments of pain, physical function, and satisfaction two to seven years after the knee replacement. Of the 1486 patients who were eligible for inclusion in the survey, 1193 (80.3 per cent) responded. The mean age of the respondents was 72.6 years. Eight hundred and forty-nine respondents (71.2 per cent) were white, and 849 (71.2 per cent) were women. The participants reported that they had little or no pain in the knee at the time of the survey, regardless of the age at the time of the knee replacement, the body-mass index, or the length of time since the knee replacement. After adjustment for potential confounding variables, predictors of better physical function after the replacement were an absence of problems with the contralateral knee, primary knee replacement (rather than revision) (Indiana sample only), and a lower body-mass index (Indiana and western Pennsylvania samples). Four hundred and fifteen (85.2 per cent) of the 487 patients in the national sample were satisfied with the result of the knee replacement. In what we believe to be the first community-based study of the outcome of knee replacement, patients reported having significant (p = 0.0001) and persistent relief of pain, improved physical function, and satisfaction with the result two to seven years postoperatively. The findings of the present study suggest that age and obesity do not have a negative impact on patient-relevant outcomes (pain and physical function). Dissemination of these findings has the potential to increase appropriate referrals for knee replacement and thereby reduce the pain and functional disability due to osteoarthrosis of the knee.

Clinical trials of nimodipine as a potential neuroprotector in ovarian cancer patients treated with cisplatin

Our previous randomised trial in patients with advanced ovarian cancer indicated a significant response and survival advantage for those receiving high-dose (100 mg/m2) as compared with low-dose (50 mg/m2) cisplatin in combination with cyclophosphamide (750 mg/m2). However, this was accompanied by more toxicity; peripheral neuropathy was troublesome, with 32% of patients experiencing > or = WHO grade 2 at the cisplatin dose of 100 mg/m2. Nimodipine is a calcium-channel antagonist that has provided protection from cisplatin-induced neurotoxicity in a rat model system. We performed a pilot study in 50 patients that demonstrated the feasibility of co-administration of nimodipine in a chronic oral dosing schedule with cisplatin-based chemotherapy in an open-label non-randomised trial. This led us to initiate a double-blind, placebo-controlled, randomised trial in patients with ovarian cancer, which was prematurely discontinued because of problems with nausea and vomiting, leading to poor patient compliance, that were not predicted by the pilot study. These studies did not demonstrate a neuroprotective effect for nimodipine. The primary efficacy variable, i.e, the neurotoxicity score at the end of treatment, gave a significantly lower mean for placebo patients than for nimodipine patients. This report details our experience and discusses the reasons for premature termination of the randomised trial.

Royal Society of Tropical Medicine and Hygiene Meeting at Manson House, London, 12 December 1996. HIV and pneumococcal infection in Africa. Microbiological aspects

By the 1930s several studies had shown that Streptococcus pneumoniae was an important pathogen in Nairobi (Kenya) and various risk factors for infection were recognized, including seasonally cold conditions, overcrowding and recent arrival in the city. Research into pneumococcal disease declined with the arrival of penicillin but recently interest has been rekindled by recognition of the pneumococcus as a human immunodeficiency virus (HIV)-associated pathogen and by the emergence of antibiotic resistance. The pneumococcus and its association with HIV were studied during the course of the Wellcome Trust/Kenya Medical Research Institute HIV Programme in Nairobi (1988-1993). There were generally high rates of pneumococcal disease. The pneumococcus (with tuberculosis and salmonellosis) was a major HIV-related pathogen. One study showed HIV seropositivity to confer a relative risk of 17.8 for pneumococcal infection. Recurrent infection accounted for a large proportion (25%) of disease episodes in a longitudinally studied cohort of HIV patients. There were higher pneumococcal carriage rates in HIV-positive than in HIV-negative patients (28% vs. 16%, P = 0.003). High rates of resistance were found to penicillin (25%). Molecular characterization of penicillin-resistant strains identified 11 separate clones, showing great genetic diversity in a small sample of isolates, and there was evidence of horizontal spread of penicillin-binding protein genes between separate lineages. Molecular characterization of isolates from patients with recurrent disease suggested that both relapse and reinfection might occur. There was molecular evidence of transfer of capsular genes between clones (serotype switching). The overall spectrum of serotypes resembled those reported elsewhere, most serotypes being included in the 23-valent vaccine. Higher numbered serotypes were associated with respiratory tract source and antibiotic resistance. Various methods were used to show 82% concordance between pernasal and blood isolates in pneumonia cases. HIV-seropositive patients were more prone to infection with penicillin- and tetracycline-resistant organisms than seronegative patients (penicillin, 27% vs. 7%; tetracycline, 40% vs. 17%), a difference reflected by different serotype profiles in the 2 groups. These studies highlight the importance of the pneumococcus as an HIV-related pathogen in one part of Africa. The high rates of antibiotic resistance are a cause of concern. There should be continued monitoring of resistance patterns, and assessments of the significance of pneumococcal disease made elsewhere in Africa are to be encouraged.

Caring until the end

As palliative care nurses working in a community based palliative care setting, we have found that patients and their carers (be they non-professional carers, family and/ or friends) have different needs at different times when it comes to information about illness and prognosis.

Actual versus perceived HIV status, sexual behaviors and predictors of unprotected sex among young gay and bisexual men who identify as HIV-negative, HIV-positive and untested

OBJECTIVES

To compare the prevalence and predictors of HIV sexual risk behavior among young gay and bisexual men who perceived themselves to be HIV-negative, HIV-positive, or who were untested.

DESIGN

Population-based sample of young gay and bisexual men.

METHODS

Using multi-stage probability sampling, 408 gay and bisexual men aged 18-29 years in San Francisco were recruited and interviewed, and blood samples for HIV-testing from 364 participants were obtained.

RESULTS

HIV prevalence was 18.7%, although 25% of the men who were HIV-positive did not know it. Thirty-seven per cent reported engaging in unprotected anal intercourse during the past year, including 59% of the men who knew they were HIV-positive, 35% of the men who perceived themselves HIV-negative and 28% of the untested men. Logistic regressions found similar predictors of unprotected intercourse for HIV-negatives and HIV-positives, including sexual impulsivity, substance use, sexual enjoyment and communication problems.

CONCLUSIONS

The high rates of unprotected intercourse, particularly among the HIV-positive men, attest to the urgent need for HIV-prevention interventions for young gay and bisexual men. The findings suggest that many of the important variables to target in interventions are similar for both HIV-positive and HIV-negative men.