Multiple Imputation for Partial Recording Periodontal Examination Protocols

AIM

Partial-mouth recording protocols often result in underestimation of population prevalence and extent of periodontitis. We posit that multiple imputation of measures such as clinical attachment loss for nonselected tooth sites in partial-mouth samples can reduce bias in periodontitis estimates.

METHODS

Multiple imputation for correlated site-level dichotomous outcomes in a generalized estimating equations framework is used to impute site-level binary indicators for clinical attachment loss exceeding a fixed threshold in partial-mouth samples. Periodontitis case definitions are applied to the imputed "complete" dentitions, enabling estimation of prevalence and other summaries of periodontitis for partial-mouth samples as if for full-mouth examinations. A multiple imputation-bootstrap procedure is described and applied for point and variance estimation of these periodontitis measures. The procedure is evaluated with pseudo-partial-mouth samples based on random site selection protocols of 28 to 84 periodontal sites repeatedly generated from full-mouth periodontal examinations of 3,621 participants in the 2013 to 2014 National Health and Nutrition Examination Survey (NHANES) survey.

RESULTS

Multiple imputation applied to partial-mouth samples overestimated periodontitis mean extent, defined as the number of sites with clinical attachment loss 3 mm or greater, by 9.5% in random site selection protocols with 84 sites and overestimated prevalence by 5% to 10% in all the evaluated protocols.

CONCLUSIONS

In the 2013 to 2014 NHANES data, multiple imputation of site-level periodontal indicators provides less biased estimates of periodontitis prevalence and extent than has been reported from estimates based on the direct application of full-mouth case definitions to partial-mouth samples. Multiple imputation provides a promising solution to the longstanding, vexing problem of estimation bias in partial-mouth recording, with potential application to a wide array of case definitions, periodontitis measures, and partial recording protocols.

KNOWLEDGE TRANSFER STATEMENT

Partial-mouth sampling, while a resource-efficient strategy for obtaining oral disease estimates, often results in underestimation of periodontitis metrics. Multiple imputation for nonselected periodontal sites produces pseudo-full-mouth data sets that may be analyzed and combined to produce estimates with small bias.

Prediction Model Development and Validation of 12-Year Incident Edentulism of Older Adults in the United States

INTRODUCTION

Edentulism affects health and quality of life.

OBJECTIVES

Identify factors that predict older adults becoming edentulous over 12 y in the US Health and Retirement Study (HRS) by developing and validating a prediction model.

METHODS

The HRS includes data on a representative sample of US adults aged >50 y. Selection criteria included participants in 2006 and 2018 who answered, "Have you lost all of your upper and lower natural permanent teeth?" Persons who answered "no" in 2006 and "yes" in 2018 experienced incident edentulism. Excluding 2006 edentulous, the data set (n = 4,288) was split into selection (70%, n = 3,002) and test data (30%, n = 1,286), and Monte Carlo cross-validation was applied to 500 random partitions of the selection data into training (n = 1,716) and validation (n = 1,286) data sets. Fitted logistic models from the training data sets were applied to the validation data sets to obtain area under the curve (AUC) for 32 candidate models. Six variables were included in all models (age, race/ethnicity, gender, education, smoking, last dental visit) while all combinations of 5 variables (income, alcohol use, self-rated health, loneliness, cognitive status) were considered for inclusion. The best parsimonious model based on highest mean AUC was fitted to the selection data set to obtain a final prediction equation. It was applied to the test data to estimate AUC and 95% confidence interval using 1,000 bootstrap samples.

RESULTS

From 2006 to 2018, 9.7% of older adults became edentulous. The 2006 mean (SD) age was 66.7 (8.7) for newly edentulous and 66.3 (8.4) for dentate (P = 0.31). The baseline 6-variable model mean AUC was 0.740. The 7-variable model with cognition had AUC = 0.749 and test data AUC = 0.748 (95% confidence interval, 0.715-0.781), modestly improving prediction. Negligible improvement was gained from adding more variables.

CONCLUSION

Cognition information improved the 12-y prediction of becoming edentulous beyond the modifiable risk factors of smoking and dental care use, as well as nonmodifiable demographic factors.

KNOWLEDGE TRANSFER STATEMENT

This prediction modeling and validation study identifies cognition as well as modifiable (dental care use, smoking) and nonmodifiable factors (race, ethnicity, gender, age, education) associated with incident complete tooth loss in the United States. This information is useful for the public, dental care providers, and health policy makers in improving approaches to preventive care, oral and general health, and quality of life for older adults.

Differential Misclassification of Disease under Partial-Mouth Sampling

Aim:

The effect of misclassification of a cluster-level dichotomous outcome (disease) due to partial-cluster sampling on its association with a dichotomous exposure is investigated.

Methods:

Disease (e.g., chronic periodontitis) is deemed to exist in a cluster (e.g., full mouth) when a condition of interest (e.g., pocket depth or clinical attachment loss exceeding an established threshold) is present in number and pattern across observations (e.g., tooth sites) in the cluster according to a specific criterion. When a subset of observations within each cluster is selected (i.e., partial-mouth sampling), specificity of disease is 100% (in the absence of site-level measurement error), whereas sensitivity is imperfect and generally unknown. Using conditional probability arguments, we investigate disease misclassification under partial-cluster sampling and its impact on the estimated disease-exposure association when the exposure is cluster level and measured without error.

Results:

When the probability of disease varies by exposure status, outcome misclassification at the cluster level is differential under partial-cluster sampling and depends on 1) the partial recording protocol, including the number of observations sampled and the particular sites selected in a cluster; 2) the joint probability structure of the condition within clusters; and 3) the criterion for disease. A numeric example demonstrates that disease-exposure odds ratios under partial-cluster random sampling can be biased in either direction (toward or away from the null) relative to gold-standard odds ratios under full-cluster sampling.

Conclusions:

In general, misclassification of disease is differential under partial-cluster sampling. In particular, sensitivity and negative predictive values depend on exposure status, which leads to biased inference.

Knowledge Transfer Statement:

Partial-mouth sampling causes disease misclassification probabilities, including sensitivity, to vary by exposure groups when disease prevalence differs between groups. As a result, disease-exposure associations may be under- or overestimated by standard analysis procedures for periodontal data relative to full-mouth estimates. Procedures that address bias are needed for partial-recording protocols.

Effect of home-based light treatment on persons with dementia and their caregivers

Sleep disorders are problematic for persons with dementia and their family caregivers. This randomized controlled trial with crossover evaluated the effects of an innovative blue-white light therapy on 17 pairs of home-dwelling persons with dementia and their caregivers. Subjects with dementia received blue-white light and control ('red-yellow' light) for six weeks separated by a four-week washout. Neither actigraphic nor most self-reported sleep measures significantly differed for subjects with dementia. For caregivers, both sleep and role strain improved. No evidence of retinal light toxicity was observed. Six weeks of modest doses of blue-white light appear to improve sleep in caregivers but not in persons with dementia. Greater or prolonged circadian stimulation may be needed to determine if light is an effective treatment for persons with dementia.

Changes in gingival crevicular fluid inflammatory mediator levels during the induction and resolution of experimental gingivitis in humans

AIM

The goal of this study is to characterize the changes in 33 biomarkers within the gingival crevicular fluid during the 3-week induction and 4-week resolution of stent-induced, biofilm overgrowth mediated, experimental gingivitis in humans.

METHODS

Experimental gingivitis was induced in 25 subjects for 21 days followed by treatment with a sonic powered toothbrush for 28 days. Clinical indices and gingival crevicular fluids were collected weekly during induction and biweekly during resolution. Samples were analysed using a bead-based multiplexing analysis for the simultaneous measurements of 33 biomarkers within each sample including cytokines, matrix-metalloproteinases (MMPs) and adipokines. Prostaglandin-E(2) was measured by enzyme-linked immunoadsorbant assay. Statistical testing using general linear models with structured covariance matrices were performed to compare stent to contralateral (non-stent) changes in clinical signs and in biomarker levels over time.

RESULTS

Gingivitis induction was associated with a significant 2.6-fold increase in interleukin 1-beta (IL-beta), a 3.1-fold increase in IL-1alpha and a significant decrease in multiple chemokines as well as MMPs-1, -3 and 13. All changes in clinical signs and mediators rebounded to baseline in response to treatment in the resolution phase.

CONCLUSIONS

Stent-induced gingivitis is associated with marked, but reversible increases in IL-alphaa and IL-1beta with suppression of multiple chemokines as well as selected MMPs.

The rapidity of drug dose escalation influences blood pressure response and adverse effects burden in patients with hypertension: the Quinapril Titration Interval Management Evaluation (ATIME) Study. ATIME Research Group

BACKGROUND

Antihypertensive medication doses are typically increased within several weeks after initiation of therapy because of inadequate blood pressure (BP) control and/or adverse effects.

METHODS

We conducted a parallel-group clinical trial with 2935 subjects (53% women, n=1547) aged 21 to 75 years, with Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure VI stages 1 to 2 hypertension, recruited from 365 physician practices in the southeastern United States. Participants were randomized either to a fast (every 2 weeks; n=1727) or slow (every 6 weeks; n=1208) drug titration. Therapy with quinapril, an angiotensin-converting enzyme inhibitor, was initiated at 20 mg once daily. The dose was doubled at the next 2 clinic visits until the BP was lower than 140/90 mm Hg or a dose of 80 mg was reached.

RESULTS

Pretreatment BP averaged 152/95 mm Hg. Patients with stage 2 hypertension reported more symptoms than those with stage 1. The BP averaged 140/86, 137/84, and 134/83 mm Hg in the slow group compared with 141/88, 137/85, and 135/84 mm Hg in the fast group at the 3 respective clinic visits. The BP control rates to lower than 140/90 mm Hg at the 3 clinic visits were (slow, fast, respectively) 41.3%, 35.7% (P<.001); 54.3%, 51.5% (P=.16); and 68%, 62.3% (P=.02). In the fast group, 10.7% of participants experienced adverse events vs 10.8% in the slow group; however, 21.0% of adverse events in the fast group were "serious" vs only 12% in the slow group.

CONCLUSION

Slower dose escalation of the angiotensin-converting enzyme inhibitor quinapril provides higher BP control rates and fewer serious adverse events than more rapid drug dose escalation.

Specialized dementia programs in residential care settings

The authors conducted a telephone survey in 7 states to determine the prevalence of residential care specialized dementia programs (RC-SDPs) and to identify a sample of homes (n = 56) for more detailed study. The 56 homes were site visited, and data were gathered on facility administration, therapeutic environment, and characteristics of 259 randomly selected residents. Comparison data from 138 nursing home Special Care Units (NH-SCUs) and 1,340 of their residents were obtained from 4 studies conducted in the same 7 states. RC-SDPs were smaller, provided a more homelike environment, and had a higher proportion of residents paying privately, compared with NH-SCUs. Mean levels of cognitive and physical impairment among residents were higher in NH-SCUs; prevalences of psychotropic medication use and problem behaviors were similar. Among RC facilities, small homes were more homelike, provided fewer structured activities, and charged less than larger facilities. RC-SDPs include 5 types: small, independently operated homes; multiple small homes with joint administration; larger, all-dementia facilities; SDPs operated within larger, exclusively RC facilities; and RC-SDPs in multilevel facilities.

Communication between older adults and their physicians about urinary incontinence

BACKGROUND

Urinary incontinence (UI) is a common but undertreated condition in older adults. The study objective was to determine older patients' characteristics related to communication patterns with their physicians about UI.

METHODS

Telephone surveys of a sample of patients age 60 and older who visited a primary care provider (PCP) for any reason within the past 2 months were conducted. Participating physicians included general internists and family physicians from 41 primary care practices located in the 17 counties of northwest North Carolina whose 435 incontinent and 711 continent patients completed the surveys. The main outcome measures were patients' frequency and amount of urinary leakage, being asked about incontinence, and initiating a discussion of incontinence if not asked by their PCP.

RESULTS

Age and gender were significant independent predictors of incontinence. PCPs were significantly more likely to assess incontinent women than incontinent men (21% vs 10%, p = .053). The older cohorts of older adults were significantly more likely to be symptomatic for UI than their younger counterparts. However, the younger cohorts were more likely to be screened for incontinence by their physicians.

CONCLUSIONS

Despite the publication of guidelines on improving the screening and management of UI, the problem remains common and underdetected in older adults. Physicians don't ask and patients don't tell. Interventions are needed to remind physicians to screen high risk patients and to encourage patients with UI to communicate with their physicians.

Implementation of EPA's Worker Protection Standard training for agricultural laborers: an evaluation using North Carolina data

The US Environmental Protection Agency has promulgated a Worker Protection Standard which requires that farmworkers receive pesticide safety training. The implementation of these regulations has not been evaluated. Using data collected through personal interviews with 270 Hispanic farmworkers recruited from 35 labor sites in an eight-county area, the authors analyzed the extent to which farmworkers received pesticide safety training, characteristics of the training, and variations in knowledge and safety behavior. Approximately a third of the farmworkers reported having ever received information or training on pesticide safety, and 25.6% reported having received training in the year in which they were interviewed. Workers with H2A visas were significantly more likely to have received training than workers without these visas. The training received varied in location, duration, and language. Most included the use of a video, as well as verbal presentation, and most included printed materials. However, few workers knew the ways in which they could be exposed to pesticides or reported using any method to protect themselves from pesticide exposure.

Comparison of the efficacy of dihydropyridine calcium channel blockers in African American patients with hypertension. ISHIB Investigators Group. International Society on Hypertension in Blacks

BACKGROUND

Hypertension is a prevalent disease among African Americans, and successful treatment rates are low. Since calcium channel blockers are well-tolerated and efficacious in African Americans, we undertook this study to compare the efficacy, safety, and tolerability of 3 commonly prescribed calcium channel blockers: amlodipine besylate (Norvasc), nifedipine coat core (CC) (Adalat CC), and nifedipine gastrointestinal therapeutic system (GITS) (Procardia XL).

METHODS

One hundred ninety-two hypertensive patients across 10 study centers were randomly assigned to double-blind monotherapy with amlodipine besylate (5 mg/d), nifedipine CC (30 mg/d), or nifedipine GITS (30 mg/d) for 8 weeks. Patients not achieving therapeutic response after 4 weeks had their dose doubled for the next 4 weeks. The primary end point was a comparison of the average reduction (week 8 minus baseline) in 24-hour ambulatory diastolic blood pressure (DBP). Secondary end points included a comparison of average 24-hour ambulatory systolic blood pressure (SBP), office SBP or DBP reduction, responder rates, safety, and tolerability.

RESULTS

One hundred sixty-three patients were evaluable for efficacy after 8 weeks. There was no significant difference in the average 24-hour ambulatory DBP (-8.5, -9.0, and -6.1 mm Hg, respectively) or SBP (-14.3, -15.7, and -11.8 mm Hg, respectively) reduction. Average office SBP and DBP were reduced to a comparable degree (19-22 mm Hg [P =.50] and 12-14 mm Hg [P =.51], respectively). Responder rates (DBP <90 or reduced by > or = 10 mm Hg) were similar (P = .38). Discontinuation rates and adverse event frequency were distributed similarly across the 3 treatment groups.

CONCLUSION

The efficacy, safety, and tolerability of the 3 dihydropyridine calcium channel blockers are equivalent in African Americans with stages 1 and 2 hypertension.

The quality of life of older adults with urinary incontinence: determining generic and condition-specific predictors

Urinary incontinence (UI) is an unpleasant problem for many adults. This study determined the importance of demographic, health and incontinence variables for the generic and incontinence-specific quality of life (QoL) of older adults (age > or = 60 years). Telephone surveys of adults reporting at least weekly episodes of UI (n = 435) were conducted as part of a randomized, controlled trial. Logistic regression analyses showed that the predictors of generic and incontinence-specific QoL differed. Life satisfaction, a generic outcome, was predicted by education, the number of days in bed due to health problems, the number of days not feeling well and the amount of urine lost. Generic health was related to education, the number of days sick in the previous 30 days and the number of days health issues restricted activities. The incontinence-specific QoL outcomes were predicted by age, mobility difficulties, the amount of urine lost, the frequency of UI, and the number of daytime and night-time voids. The specific QoL measures provide a different profile of those most affected in this sample than that obtained by the generic measures. The most affected are younger persons with severe urine loss. Older persons may have other conditions impinging on QoL and may have adapted behaviourally and psychologically to urine loss.

Predictors of fear of falling in dizzy and nondizzy elderly

Fear of falling may constitute an independent risk factor for disability, leading older people to unnecessarily restrict their activity. Sixty older adults with chronic dizziness and 66 healthy controls were studied to help clarify the interrelationships among demographic factors, psychological status, physical health, and fear of falling. Chronic dizziness was strongly associated with fear of falling; among dizzy patients, nearly half (47%) expressed fear of falling, in comparison with 3% of controls. In participants with dizziness, 3 factors predicted fear of falling: an activity of daily living score, the revised Symptom Checklist 90 Depression (Derogatis, 1983) score, and stability when standing with feet together. These results support the concept that fear of falling is multiply determined and that psychological factors play a major role in influencing the symptoms and responses in many older patients with dizziness.

Predictors of fear of falling in dizzy and nondizzy elderly

Fear of falling may constitute an independent risk factor for disability, leading older people to unnecessarily restrict their activity. Sixty older adults with chronic dizziness and 66 healthy controls were studied to help clarify the interrelationships among demographic factors, psychological status, physical health, and fear of falling. Chronic dizziness was strongly associated with fear of falling; among dizzy patients, nearly half (47%) expressed fear of falling, in comparison with 3% of controls. In participants with dizziness, 3 factors predicted fear of falling: an activity of daily living score, the revised Symptom Checklist 90 Depression (Derogatis, 1983) score, and stability when standing with feet together. These results support the concept that fear of falling is multiply determined and that psychological factors play a major role in influencing the symptoms and responses in many older patients with dizziness.

Which primary care patients with dizziness will develop persistent impairment?

OBJECTIVE

To determine which factors identifiable during an office visit for dizziness predict chronic impairment from dizziness 3 months later.

DESIGN

A prospective cohort study with 3-month telephone follow-up.

SETTING

Nine primary care office practices in North Carolina.

SUBJECTS

117 adults who presented to primary care practices because of dizziness.

OUTCOME MEASURES

Our outcome of interest, restriction of daily activities due to dizziness 3 months after the enrollment visit, was characterized using three different but correlated self-reported measures. Independent analytic models tested the relationship between demographic variables, health status, psychological state, and dizziness characteristics at baseline and our three measures of activity restriction due to dizziness.

RESULTS

A two-stage logistic regression analysis identified the following baseline characteristics to be independent predictors in one or more models of activity-limiting dizziness at 3 months: dependency in instrumental activities of daily living (odds ratio [OR] = 11.1, P = .002); a high anxiety score (OR = 5.7, P = .003); self-rating of health as fair or poor (OR = 3.2, P = .042); the presence of three or more chronic conditions (OR = 1.9, P = .022); interference from chronic conditions (OR = 1.7, P = .012); dizziness duration of greater than 1 year (OR = 20.9, P < .001); frequent dizziness (OR = 4.3, P = .016); subjective imbalance (OR = 4.7, P = .012); and activity limitation due to dizziness (OR = 11.7, P < .001).

CONCLUSION

To estimate the prognosis and clinical significance of dizziness complaints, primary care physicians should take into account not only the characteristics of the patient's dizziness but also the patient's baseline health status and psychological state.

Solute distribution between vacuole and cytosol of sugarcane suspension cells: Sucrose is not accumulated in the vacuole

The compartmentation of solutes in suspension cells of Saccharum sp. during different growth phases in batch culture was determined using CuCl2 to permeabilize the plasma membrane of the cells. The efflux of cytosolic and vacuolar pools of sugars, cations and phosphate was monitored, and the efflux data for phosphate were compared and corrected using data from compartmentation analysis of phosphate as determined by (31)P-nuclear magnetic resonance spectroscopy. The results show that sucrose is not accumulated in the vacuoles at any phase of the growth cycle. On the other hand, glucose and fructose are usually accumulated in the vacuole, except at the end of the cell-culture cycle when equal distribution of glucose and fructose between the cytosol and the vacuole is found. Both Na(+) and Mg(2+) are preferentially located in the vacuoles, but follow the same tendency as glucose and fructose with almost complete location in the vacuole in the early culture phases and increasing cytosolic concentration with increasing age of the cell culture. Potassium ions are always clearly accumulated in the cytosol at a concentration of about 80 mM; only about 20% of the cellular K(+) is located inside the vacuole. Cytosolic phosphate is little changed during the cell cycle, whereas the vacuolar phosphate pool changes according to total cellular phosphate. In general there are two different modes of solute compartmentation in sugarcane cells. Some solutes, fructose, glucose, Mg(2+) and Na(+), show high vacuolar compartmentation when the total cellular content of the respective solute is low, whereas in the case of ample supply the cytosolic pools increase. For other solutes, phosphate and K(+), the cytosolic concentration tends to be kept constant, and only excess solute is stored in the vacuole and remobilized under starvation conditions. The behaviour of sucrose is somewhat intermediate and it appears to equilibrate easily between cytosol and vacuole.

Sucrose uptake into vacuoles of sugarcane suspension cells

Uptake of sucrose into vacuoles of suspension cells of Saccharum sp. (sugarcane) was investigated using a vacuole-isolation method based on osmotic- and pH-dependent lysis of protoplasts. Vacuoles took up sucrose at high rates without the influence of tonoplast energization on sucrose transport. Neither addition of ATP or pyrophosphate nor dissipation of the membrane potential or the pH gradient by ionophores changed uptake rates appreciably. Generation of an ATP-dependent pH gradient across the tonoplast was measured in vacuoles and tonoplast vesicles by fluorescence quenching of quinacrine. No H(+) efflux could be measured by addition of sucrose to energized vacuoles or vesicles so that there was no evidence for a sucrose/H(+) antiport system. Uptake rates of glucose and other sugars were similar to those of sucrose indicating a relatively non-specific sugar uptake into the vacuoles. Sucrose uptake was concentration-dependent, but no clear saturation kinetics were found. Strict dependence on medium pH and inhibition of sucrose transport by p-chloromercuriphenylsulfonic acid (PCMBS) indicate that sucrose uptake into sugarcane vacuoles is a passive, carrier-mediated process.

Analysis of the reaction products from incubation of sugarcane vacuoles with uridine-diphosphate-glucose: no evidence for the group translocator

Isolated sugarcane (Saccharum spp. hybrid H50-7209) vacuoles incorporate radioactivity during incubation with labeled UDP-glucose by a mechanism which was postulated to be responsible for sucrose storage in the vacuoles (UDP-glucose group translocator). Analysis of the reaction products in the medium revealed that several enzymic processes are going on during incubation with UDP-glucose such as production of hexose phosphates, UMP, and sugars, all of which seem unrelated to the incorporation of radioactivity into vacuoles. The incorporated radioactivity was identified mainly as (1-->3)-beta-glucan (callose) of polymerization grades up to more than 20. Callose occurs as a contaminant at the surface of isolated vacuoles coming from the plasmalemma. The properties of UDP-glucose incorporation into the vacuolar preparation compared favorably with known properties of callose synthase. The low mol wt glucans that are found are probably degradation products of labeled callose due to hydrolases, which are liberated by centrifugation of vacuoles. The labeled disaccharide, which chromatographically had been formerly identified as sucrose, is laminaribiose. No sucrose (or sucrose phosphate) could be identified in the vacuole preparation after incubation with UDP-glucose. Thus, the mechanism of sucrose storage in sugarcane vacuoles is still open.

Solubilization and purification of the ATPase from the tonoplast of Hevea

The tonoplast-bound ATPase of Hevea brasiliensis (caoutchouc tree) was solubilized with dichloromethan and purified 100-fold with two ammonium sulfate precipitation steps and a G-200 gel filtration step. The resulting ATPase activity eluted according to a molecular mass of approximately 200 kDa and chromatographed at an isoelectric pH of 5.3. Subunits of molecular mass 110 kDa, 68 kDa, 24 kDa and 12 kDa appeared after treatment with 1% sodium dodecyl sulfate or spontaneously during storage of the solubilized ATPase. Dodecyl sulfate/polyacrylamide gel electrophoresis yielded four polypeptides of molecular mass 54 kDa, 66 kDa, 23 kDa and 13 kDa. From protein determination by ultraviolet absorption and Coomassie stain it appears that the 54-kDa and the 66-kDa polypeptides exist in multiple copies. No close resemblance to the membrane-bound ATPase of mitochondria, plastids, plasmalemma, chromaffin granules and synaptic vesicles is seen. No antibody cross-reaction to F1 of bacteria is observed. Therefore it is concluded that the vacuolar ATPase represents a novel type of ATPase. Many properties of the tonoplast-bound ATPase such as pH-dependence, substrate specificity, ion-dependence and inhibitor sensitivity did not change when the enzyme had been solubilized and purified. The phosphatase activity was lost during the purification procedure. The stimulation of ATP-hydrolysis in tonoplast vesicles by uncouplers and ionophores was absent in the solubilized ATPase, and also the stimulation by chloride was significantly reduced. Anion channel blockers, such as triphenyltin and 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene, which are strong inhibitors of membrane-bound ATPase, fully or partly lost their inhibiting effect after solubilization of the ATPase. These results are interpreted to indicate that ionophores do not directly affect the ATPase molecule, whereas chloride might have a small direct effect on the ATPase besides its effect as a permeating anion.