4118Cisplatin therapy as a risk factor for incident atrial fibrillation

Background

Although aging is a major contributor to the rising epidemic of atrial fibrillation (AF), increased numbers of cancer survivors who suffer from chemotherapy and radiotherapy mediated cardiovascular disease also appear to be especially vulnerable to developing the arrhythmia. Currently, little is known about the long-term risk of AF in patients treated with these two treatment modalities for cancer.

Purpose

To define the incidence and prevalence of AF in a thoracic tumour cohort following radiotherapy and chemotherapy.

Methods

We conducted a retrospective study from the electronic health records (EHR) of patients who had a primary tumour of the breast and lung. Patients with AF, radiotherapy or chemotherapy prior to cancer diagnosis were excluded. All patients were followed for incident AF until last censoring or death using a validated AF algorithm (positive predictive value 96%). Radiation oncology treatment reports were reviewed and chemotherapy data was extracted from the EHR and manually reviewed for 43 chemotherapeutic agents.

Results

In the tumour registry, 17,402 patients were identified by histological and pathological reports. We examined 3,336 patients with a thoracic tumour diagnosis (breast and lung) with a mean age of 62.7±12.5 (SD) years. The AF incident rate for breast and lung cancer was 1.2 and 13.5 cases per every 100 persons with a cumulative rate of 2.49 and 0.67 respectively. We observed an overall AF prevalence of 3.4% and 7.4% in the breast and lung cohorts respectively. The average follow-up duration was 4.69 years (0.0–17.8 years) in breast cancer and 1.36 years (0.0–13.9 years) in lung cancer patients. A Cox regression model revealed no association between radiotherapy and AF in either cancer type (breast: P=0.18 and lung: P=0.16). However, patients who received cisplatin had 4-fold increased risk of developing AF after covariate adjustment (HR = 4.22, 95% CI: 0.10–17.85, P=0.05).

Conclusions

We show for the first time in a large thoracic tumour registry and using the EHR that patients treated with cisplatin were more likely to develop AF. Additional studies are needed to validate our findings and to further investigate the underlying mechanisms of these cardiotoxic effects.

Acknowledgement/Funding

This work was supported in part by grants from the AHA 17MCPRP33420153 (Brandon Chalazan) and NIH/NHLBI R01 HL092217 and HL138737 (Dawood Darbar).

Effect of germination of finger millet on nutritional value of foods and effect of food supplement on nutrition and anaemia status in Tanzanian children

Inadequate dietary intake, often combined with an infection can lead to malnutrition that often manifest as growth failure or deficiency of essentials nutrients including iron leading to iron deficiency anaemia. In an effort to investigate diet in relation to nutrition status of children, diet and dietary intake were investigated in rural Tanzania. The effect of germination of finger millet based food recipe on its nutritional value was evaluated. The food consisted of finger millet flour, kidney beans, ground peanuts and dried mangoes at predetermined proportions of 75:10:10:5 respectively. Dietary habits of young children were investigated and effects of a fortified food supplement and the cereal based recipe on nutrition status of children were investigated. The two diets were then supplemented to children for 6 months and changes on anaemia and anthropometrical indices of children were evaluated at follow up periods. To assess anaemia and iron status, haemoglobin (Hb), haematocrit (Hct), erythrocyte protoporphyrin (EP) and serum ferritin (SF); and weights and heights were measured to assess growth. A significant improvement in nutrient density was noted in processed cereals. Bioavailability of iron in cereal based diet increased from 0.75 +/- 18 to 1.25 +/- 41 mg/100 g (P = 008), viscosity was significantly raised by 12% and phytate concentration was reduced from 4.5 +/- 0.5 to 4.1 +/- 0.5 mg/g (P = 0.03). Significantly lower intake of iron was observed in schoolchildren with Hb < 11.5 g/dl) compared to those who were normal. Total iron intake was 22+/- 7 and 27 +/- 13 mg/day, respectively (P < 0.05). There was a significant correlation between iron intake and serum ferritin (r = 0.233, P < 0.05). After six months of supplementing children with the fortified beverage a significantly larger increase in haemoglobin concentration was shown in the fortified group than in the non-fortified group (a difference of 6.2 versus 3.2 g/dl respectively). Supplementing infants with the germinated cereal based food supplement showed a general improvement on Hb status and growth that was not significantly different to that in the control group (P > 0.05). In conclusion, consumption of foods with low iron bioavailability is a major cause of anaemia. Germination improves the nutritional value of foods however there is need to fortify such processed foods for infant feeding.

Recto-urethral fistula following brachytherapy for localized prostate cancer

OBJECTIVE

The use of prostate brachytherapy (BT) in the management of prostate cancer is increasing. BT is often chosen because of its perceived lower toxicity when compared with other radical therapy options. Rarely however serious complications can occur. One such complication is recto-urethral fistula (RUF). We report the incidence of RUF following BT at our centre and review the potential factors in fistula development.

METHOD

A prospectively collected database was used to identify cases of RUF among 1455 patients treated with prostate BT at a single UK centre with at least 2 years of follow up. This included patients treated with BT monotherapy, as well as those treated with BT combined with external beam radiotherapy and BT used as salvage as all these groups have a higher incidence of RUF. Implant dose and volume characteristics for those patients, their co-morbidities and history of endoscopic procedures were recorded.

RESULTS

Recto-urethral fistula was identified in three (0.2%) patients, occurring at 19-27 months following BT. All these patients had BT monotherapy. All three patients had rectal symptoms after their BT and had been investigated with endoscopy and low rectal biopsy. Subsequent surgical management with faecal and/or urinary diversion was required. On review of patients' BT details, radiation dose and volume parameters were higher on the postprocedure CT calculations than had been suggested by the preimplant plan. No other predisposing risk factors for RUF were identified.

CONCLUSION

The incidence of RUF in our population is low. RUF following BT has been associated with rectal biopsy in previous series and this is confirmed in our report. Gastrointestinal specialists should not perform biopsy of the anterior rectum in patients who have had BT unless there is a very high clinical suspicion of malignancy.

A randomised study of whole-breast vs tumour-bed irradiation after local excision and axillary dissection for early breast cancer

AIMS

Whole-breast radiotherapy (WBRT) after conservative surgery for early breast cancer is a routine standard of care. Despite this, a number of uncertainties in management still exist. Over recent years, a number of new technologies have allowed the development of partial-breast irradiation, with the intention of improving the risk-benefit relationship of routine breast radiotherapy. We report the results of a trial comparing partial- with WBRT, with prolonged follow-up.

MATERIALS AND METHODS

Between 1986 and 1990, 174 women were randomised to receive conventional whole-breast radiotherapy (WBRT) (40 Gy in 15 fractions), with a tumour-bed boost or partial-breast irradiation by a variety of techniques. Recruitment was problematic, and the trial closed prematurely well before meeting its recruitment target.

RESULTS

A trend was observed towards higher local recurrence and a higher locoregional recurrence rate after irradiation of the tumour bed alone. Distant recurrence and survival were the same.

CONCLUSIONS

Conclusions are limited in view of the failure to complete accrual of the target of 400 participants, and in the context of the techniques of partial-breast radiotherapy used during this study, which would not compare with those in current use. Tumour-bed irradiation alone cannot currently be recommended as routine treatment outside the context of clinical trial.

Sustaining safe and acceptable bowel care in spinal cord injured patients

This article aims to increase understanding of the bowel care needs of patients with spinal cord injury. Spinal cord injury centres provide expert bowel management for these patients but healthcare staff in general hospitals may not be familiar with the techniques required.

Re-audit of radiotherapy waiting times 2003

AIMS

There has been increasing concern, by clinical oncologists in the UK, about the continuing long waiting times for radiotherapy treatment. An audit of patients starting treatment in 1 week in 2003 was carried out to determine waiting times and to compare current results with those obtained from a similar audit in 1998.

MATERIALS AND METHODS

All centres in the UK completed the audit, which recorded waiting-list status and treatment intent for all new treatments started in 1 week, date of booking form completion and fractionation scheme used.

RESULTS

Waiting times have lengthened in most centres for all categories of patients although, for palliative treatments, there was no additional increase in median waiting time compared with the last audit. Fewer patients in all categories are being treated within the Joint Collegiate Council for Oncology (JCCO) guidelines. Single-fraction treatments are now common for palliation. Most adjuvant treatment uses one of three prescriptions. In each Strategic Health Authority (StHA), the same proportion of the total number of patients with cancer seemed to be given radiotherapy. There was no obvious simple correlation of radiographer, physicist or treatment machine numbers with waiting times.

CONCLUSION

The results of this survey suggest a continuing mismatch between capacity and demand. Increased complexity of radical treatments, and possibly more patients being referred for treatment, may have been offset in part by reduced fractionation for palliation.

Retrospective Detection of Exposure to Sulfur Mustard: Improvements on an Assay for Liquid Chromatography-Tandem Mass Spectrometry Analysis of Albumin/Sulfur Mustard Adducts

We here report on the further development of the method comprising the pronase digestion of albumin alkylated by sulfur mustard and the subsequent mass spectrometric analysis of an adducted tripeptide. This includes significant improvements in both the albumin isolation procedure and the automation of the microliquid chromatography-electrospray-tandem mass spectrometric analysis. We also report on the results of a small reference range study, in which we have established that there are no detectable interferences in sera from unexposed individuals.

Brachytherapy boost to the tumour bed in high risk patients after limited surgery for breast cancer

The results of treatment for 174 patients at high risk of local recurrence, referred for radiotherapy after conservative surgery for early breast cancer, are evaluated. Microscopic margin involvement, extensive carcinoma in situ, and vascular/lymphatic invasion were the main risk factors for local recurrence. Whole-breast irradiation (40 Gy in 15 fractions over 3 weeks) followed with a brachytherapy boost (Ir192 wire implant or PDR Ir192) of 25 Gy was applied. Median follow-up was 80 months. The actuarial 6-year overall survival rate was 91% and the within breast recurrence-free survival was 88%. The most common risk factor among those recurring within the breast was involved surgical margins (13 out of 17). Cosmesis was reported to be good or excellent in 79% of cases. In patients at high risk for local recurrence, tumour-bed boost with brachytherapy can provide satisfactory local control after limited surgery and external radiotherapy.

Effect of micronutrient fortified beverage on nutritional anaemia during pregnancy

OBJECTIVE

To evaluate the efficacy of a multiple micronutrient fortified beverage containing eleven nutrients at physiological levels in prevention of anaemia and improving iron and vitamin A status during pregnancy.

DESIGN

A randomised double blind placebo controlled study.

SETTING

Mpwapwa and Kongwa Districts in Dodoma Region of Tanzania.

SUBJECTS

Five hundred and seventy nine pregnant women were screened for entry into the study and 439 women who met the study criteria were enrolled.

INTERVENTIONS

Study participants received either a fortified (F) or non-fortified (NF) orange flavoured drinks identical in appearance, provided in two self administered servings per day for an eight week period.

MAIN OUTCOME MEASURES

Comparison of haemoglobin (Hb), serum ferritin (SF) and serum retinol (SR) at baseline and follow up.

RESULTS

After eight weeks of supplementation, the F group (n=129) had a significantly higher Hb increase of 0.86 g/dL compared to 0.45 g/dL in the NF group (n=130) p<0.0001. Gestational age at entry into the study, moderated the effect on Hb of the fortified drink. Women at earlier gestational age upon entry, had a higher rise in Hb than women of late gestational age (0.8 g/dL versus 0.04 g/dL rise respectively, p=0.038, n=188). The risk of being anaemic at the end of the study for those in the F group was reduced by 51% (RR=0.49, CI=0.28 to 0.85). Iron stores (by serum ferritin levels) increased by 3 microg/L in the F group (p=0.012) and a decrease of 2 microg/L in the NF group (p=0.115). The follow up ferritin concentration depended on initial ferritin level. Regardless of treatment group, serum retinol concentrations were significantly higher in mothers who had delivered. Mothers who had adequate levels at entry benefited more from the supplement than those with low levels (0.26 micromol/L versus no significant difference).

CONCLUSIONS

The multiple micronutrient-fortified beverage given for eight weeks to pregnant women improved their haemoglobin, serum ferritin and retinol status. The risk for anaemia was also significantly reduced. The important predictors of Hb increase at follow up were the fortified beverage, baseline Hb, serum retinol, baseline ferritin and gestational age at entry into study. Anthropological research showed that the beverage was highly acceptable and well liked.

Micronutrient dietary supplements--a new fourth approach

Currently the three main widely used strategies to control micronutrient deficiencies are food diversification, fortification, and consumption of medicinal supplements. In Tanzania a fourth strategy has been evaluated in school children, and is to be studied in pregnant and lactating women. The dietary supplement comes in the form of a powder used to prepare a fruit flavored drink. Children consumed for six months 25 grams per school day attended, the powder being added to 200 ml of water. The dietary supplement provides between 40 and 100 percent of the RDA of 10 micronutrients, which includes iron, vitamin A and iodine. Unlike medicinal supplements it provides the multiple vitamins and minerals in physiologic, not megadoses. In a well conducted randomized double blind placebo controlled trial, a dietary supplement in the form of a fortified powder fruit drink produced statistically significant differences not only in vitamin A and iron status, but also in the growth of young school age children.

Evaluating cost center productivity

The monthly and yearly productivity summaries were developed and applied to a computer spreadsheet to aid the nurse manager in better understanding and communicating budget issues for diverse ambulatory care departments. A computerized spreadsheet using a commercially available personal computer program, such as Lotus, Quattro Pro, or Excel, can be used to more quickly and accurately track and summarize monthly budget reports. The data can be entered into the spreadsheet either manually or imported by query from the financial mainframe system. Contact your agency's finance or information department for information on how to accomplish this. Periodically acuity and resources should be measured and compared with quality monitors to maintain standards. For the past 10 years, our facility has successfully used this tool to make more informed decisions by identifying trouble spots early, and taking corrective action to avoid crisis management.

Shared governance: time to consider the cons as well as the pros

AIMS

This paper aims to provide a critical appraisal of an approach to the management and organization of nursing work known as shared governance (SG).

BACKGROUND

This approach has its origins in the USA, where, during the past 20 years it has become increasingly influential. The advocates of SG claim that it can, inter alia, improve recruitment and retention rates, boost morale, and help raise clinical skills. Little wonder that SG in now beginning to make significant inroads into the NHS. ORIGIN OF INFORMATION: However, a trawl through the extensive US literature, using printed and online (e.g. BIDS, CINHAL, MEDLINE, etc.) bibliographical sources, suggests that the claimed benefits of SG should be treated with caution.

KEY ISSUES

Much of the existing published research appears to be both methodologically flawed and lacking in any critical edge. While many researchers and commentators appear only too willing to highlight what they see as the promise of SG, they shy away from exploring any potential pitfalls. One consequence of this is that many of the putative benefits SG is said to confer, may in fact be more apparent than real.

CONCLUSIONS

Nurses and nurse managers need to be apprised of and consider seriously, the possible cons as well as the potential pros of SG, if any promise it may have is to be realized.

Short-term morbidity and acceptability of 125iodine implantation for localized carcinoma of the prostate

OBJECTIVE

To report the short-term morbidity and acceptability of the first 50 patients treated with the percutaneous implantation of radioactive iodine seeds for localized carcinoma of the prostate at the Cookridge Hospital.

PATIENTS AND METHODS

Fifty patients were treated with transrectal ultrasonography-guided percutaneous implants with radioactive (125I) iodine seeds for localized carcinoma of the prostate. The mean hospital stay was 36 h and most patients were able to return to work or normal activity within one week of implantation.

RESULTS

All patients developed urethritis which was most marked within the first 3 months of treatment; 8% of patients developed acute retention which resolved after temporary catheterization. At 3 months, 36% of patients still had moderate frequency and 18% moderate dysuria, but by 12 months these had resolved and only 5% of patients still complained of moderate nocturia. There were no cases of incontinence. The incidence of proctitis was very low, with only 2% still complaining of moderate symptoms at one year. Of those potent before implantation, 72% retained potency at one year.

CONCLUSIONS

Although it is too early to comment either on late morbidity or on outcome, the results of this study show a side-effect profile similar to that reported by other centres using the same technique.

Prostate brachytherapy

In recent years there has been an increase in the number of centres, especially in the USA, using prostate brachytherapy as a means of treating localised prostate cancer. Several centres now have medium term follow up data of large numbers of patients treated with this technique suggesting that outcome in terms of tumour control may be comparable to patients treated surgically. This review summarises results from different brachytherapy series and outlines some of the possible advantages of this technique compared with current conventional treatments for localised prostate cancer.

Crisis beds: the interface between the hospital and the community

The main role of the crisis unit at a state psychiatric hospital was found to be the provision of brief hospitalisation for patients with adjustment disorders and personality disorders. The four bed crisis unit treated 14% of all patients admitted to the hospital, with an average length of stay less than three days. A study of 78 crisis unit patients found that 77% were able to be discharged directly to the community, and only 18% were readmitted during the following six months.

Quality assurance in brachytherapy: the role of the ICRU in achieving uniformity in dose and volume specification for reporting

A quality assurance programme in brachytherapy implies a general consensus on the method of dose and volume specification for reporting. This in turn implies a consensus on certain definitions of terms and concepts. For several decades, the ICRU (International Commission on Radiation Units and Measurements) has been actively involved in an effort to reach a consensus between different brachytherapy centres worldwide, and to improve uniformity in reporting. The ICRU has prepared two reports containing recommendations for reporting brachytherapy treatments. The first, report #38 published in 1985, deals with intracavitary therapy in gynecology. The second deals with interstitial therapy, and is now in press. A summary of these two ICRU reports is presented here. Some definitions of terms and concepts are first recalled and discussed: Total Reference Air Kerma (TRAK), gross tumor volume (GTV), clinical target volume (CTV), treated volume, mean central dose, dose uniformity parameters, etc. Specific recommendations for reporting interstitial and intracavitary brachytherapy are then presented.

Split course radiotherapy for bladder cancer in elderly unfit patients

Between 1980 and 1987, 89 patients with T1-T4 carcinoma of the bladder were treated with a split course of external beam radiotherapy. All patients were felt to be unsuitable for a prolonged course of radical radiotherapy because of age and/or poor general health. The intention was to provide local control. The majority of patients were treated with 10-12 fractions, with a mean dose of 45 Gy (range 31.5-57.7), within a mean overall time of 48 days. Of the 89 patients only 62 were assessable with a median follow-up of 110 months (range 64-157). In the remainder, poor health, poor performance status, or early (< 3 months) death did not allow assessment of tumour control. Complete remission was achieved in 28/89 (31%) patients. This was highly dependent on T stage: 56% T1/T2, 30% T3a/T3b, 5% T4. Median survival for patients with Stage T1/T2, T3a/T3b and T4 disease was 22, 10 and 8 months respectively. Acute grade 1-2 radiation reactions occurred in 60% of these patients, and only 5/62 (8%) experienced grade 2-3 late complications, assessed according to the RTOG scoring system. No patient had more severe treatment related morbidity.

Potential disadvantages of post-operative adjuvant radiotherapy after anterior resection for rectal cancer: a pilot study of sphincter function, rectal capacity and clinical outcome

The aim of this study was to try to gauge the functional effect of post-operative adjuvant radiotherapy after potentially curative anterior resection for carcinoma of the rectum. Anorectal function was studied both in the laboratory and clinically in 59 patients, a median of 12 months (range 6-96) after operation. Nine patients received post-operative radiotherapy and 50 matched patients were treated by surgery alone. Though maximum resting anal pressures and maximum squeeze pressures were similar in the two groups of patients, the length and pressure profile of the anal sphincter were both markedly abnormal after radiotherapy. The capacity and compliance of the neorectum were diminished significantly after radiotherapy (maximum tolerated volume 53 ml vs 110 ml after surgery alone, P = 0.008, compliance 1.5 ml/cm H2O vs 3.7 ml/cm H2O after surgery alone, p = 0.018) and the amount of distension of the neorectum required to produced maximum inhibition of the anal sphincter during the rectoanal inhibitory reflex was also significantly diminished after radiotherapy (P = 0.005). Clinical anorectal function was worse among patients who had received radiotherapy, a greater proportion of whom experienced both urgency of defaecation and varying degrees of incontinence. Major faecal leakage necessitating the use of a pad was recorded in 3 of the 59 patients after radiotherapy (one of whom required a permanent colostomy), but in only 5 of 50 patients after surgery alone.

Report on the clinical effects of inadvertent radiation underdosage in 1045 patients

Between Autumn 1982 and Winter 1991, 1045 patients received lower doses of radiation than were prescribed for the treatment of their cancers because of a miscalculation of radiation doses. This occurred as a result of the introduction of a new technique of treatment planning. An error in the application of the planning system lead to an underdosage of radiation of between 5 and 35%. In patients who received radiation alone for radical treatment a dose reduction of 20% or more resulted in a lower than expected local control rate. The effects were less marked in patients who were treated by combinations of surgery and radiation and in those with a very high rate of distant metastases. In 1991, a new computer planning system was installed and a discrepancy was discovered between the new plans and those from the previous system. Further investigation revealed that the original planning system already contained within it a correction factor for the tumour to skin distance and that systematically reapplying this correction had resulted in underdoses of radiation being delivered to patients for nearly 10 years. During the 9-year period of this dose miscalculation only 6% of patients treated in the department were treated with the isocentric technique; for many of those it formed only a part of their treatment.

Guaranteeing real-time response with limited resources

Unanticipated problems detected by patient-monitoring systems may sometimes require real-time response in order to provide high-quality care and avoid catastrophic outcomes. In this paper, we present an approach for guaranteeing a response to such events by a monitoring agent even in situations where we have limited problem-solving resources. We show that an action-based hierarchy can accomplish this goal. We also analyze the performance of this hierarchy under varying resource availability and discuss decision-theoretic approaches to enable us to best structure such a hierarchy. We also describe an implementation of these ideas, called ReAct, in the BB1 architecture. All the ideas are illustrated with examples from the surgical intensive care unit (SICU).

The use of discriminant analysis to guide palliative treatment for lung cancer patients

The aim of this study was to develop a prognostic index for patients with inoperable non-small cell lung cancer which could predict survival to 3 months. This would enable less radiation dose to be given to patients where prognosis is limited by occult metastases, giving rise to less treatment morbidity and raising the therapeutic ratio. Data on 18 known prognostic factors were collected on 96 patients. Performance status, lymphocyte count, weight loss and extent of disease were the most predictive factors and were combined into an index. Logistic discriminant analysis was employed to give a numerical score of likelihood of survival to 3 months, ranging from 0 (not likely) to 1 (certain). In this first set of 96 patients, 16 deaths were observed before 3 months, of which 6 were predicted. There was one false positive prediction. Overall accuracy of prediction was therefore 89% with 99% specificity. The same 4 prognostic factors were measured on a second set of 80 patients. Nineteen died before 3 months, of which 5 were predicted with 2 false positives, giving an overall accuracy of 80% and 97% specificity. A probability of survival of less than or equal to 0.2, although highly specific, was only applicable to 9% of patients and this was the limiting factor in the clinical usefulness of the test. A 16-branch tree diagram allows any patient to be assigned a risk factor based on the four predictive factors at the first clinic attendance. Use of the index could encourage more rational prescribing of radiation dose.

Prosthodontists' preferences in preprosthetic surgery

A survey of members of the Federation of Prosthodontic Organizations was done to determine their opinions about various preprosthetic surgical procedures used to treat patients with alveolar atrophy of the maxilla and mandible. In most instances there was lack of consensus, indicating a need for consultation and close cooperation between the oral and maxillofacial surgeon and the prosthodontist in the management of individual patients.

Problems associated with iridium-192 wire implants

Three incidents are reported, from different radiotherapy centres, in which an implanted iridium-192 wire remained in the tissues of a patient after withdrawal of the plastic tubing in which it was contained. In each case the instrument used to cut the wire had probably formed a hook on the end of the wire which caused it to catch in the tissues. Detailed recommendations are made for avoiding such incidents in the future, the most important of which is that the patient should be effectively monitored after the supposed removal of all radioactive sources.

Aliphatic ketones are acetylcholinesterase inhibitors but not transition state analogs

A number of C4--C9 aliphatic ketones are acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) inhibitors, with Ki values in the 0.7--5 mM range. Comparison to analogous substrates would suggest that these ketones are transition state analogs; e.g. 2-pentanone binds to the enzyme approx. 550 times more tightly than ethylacetate. However, a number of other criteria contradict this conclusions: (1) the binding is insensitive to ketone structure: isomeric ketones, cycloalkanones, and sterically hindered ketones have similar inhibitory potencies. (2) Analogous alcohols are also good inhibitors even though they cannot form hemiketals with the enzyme. (3) Representative ketones are relatively ineffective at blocking inactivation of the enzyme by methylsulfonyl fluoride, indicating that ketones do not bind principally at the hydrolytic site. (4) A competition experiment shows that binding of tetramethylammonium chloride excludes binding of 2-pentanone, suggesting that ketones bind to the anionic rather than the hydrolytic site. Thus, observation of tight binding relative to a substrate is not a sufficient criterion to establish that an inhibitor is a transition state analog.

The Paris system in interstitial radiation therapy

As a result of almost 20 years' experience using 192Ir wires in interstitial radiation therapy, a new method of dose calculation has been evolved, which is especially suitable for the techniques employed. Because this system was developed and brought into routine use in Paris, it was called the Paris System. Its basic principles are outlined in this report and the manner in which it is used in clinical practise is explained.

The mode of binding of potential transition-state analogs to acetylcholinesterase

Phenylacetone, 4-phenyl-2-butanone, and 4-oxopentyltrimethylammonium chloride were tested as potential transition state analogs for eel acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7). Phenylacetone is a competitive inhibitor of the enzyme but not a transition state analog, since its binding constant is similar to that for the substrate phenyl acetate. 4-Phenyl-2-butanone binds 6-18 times more tightly than the inhibitors 4-phenyl-2-butanol and N-benzylacetamide and the substrate benzyl acetate and also blocks inactivation of the enzyme with methanesulfonyl fluoride. However, its binding is independent of pH in the range 5-7.5, whereas both V and V/Km for benzyl acetate hydrolysis decrease with decreasing pH in this range. These data indicate a specific but weak interaction between the ketone carbonyl and the enzyme, but probably do not justify considering this compound a transition state analog. 4-oxopentyltrimethylammonium iodide has previously been shown to bind about 125 times more strongly than the substrate acetylcholamine. It also binds about 375 times more strongly than the alcohol 4-hydroxypentyltrimethylammonium iodide. Furthermore, the ketone protects the enzyme from inactivation by methansulfony fluoride, while the corresponding quaternary ammonium alcohol accelerates this inactivation reaction. This additional information confirms that the ketone is a transition state analog.