Randomised controlled trial of thermostatic mixer valves in reducing bath hot tap water temperature in families with young children in social housing.

OBJECTIVES: To assess the effectiveness of thermostatic mixing valves (TMVs) in reducing bath hot tap water temperature, assess acceptability of TMVs to families and impact on bath time safety practices. DESIGN: Pragmatic parallel arm randomised controlled trial. SETTING: A social housing organisation in Glasgow, Scotland, UK. PARTICIPANTS: 124 families with at least one child under 5 years. INTERVENTION: A TMV fitted by a qualified plumber and educational leaflets before and at the time of TMV fitting. MAIN OUTCOME MEASURES: Bath hot tap water temperature at 3-month and 12-month post-intervention or randomisation, acceptability, problems with TMVs and bath time safety practices. RESULTS: Intervention arm families had a significantly lower bath hot water temperature at 3-month and 12-month follow-up than families in the control arm (3 months: intervention arm median 45.0°C, control arm median 56.0°C, difference between medians, -11.0, 95% CI -14.3 to -7.7); 12 months: intervention arm median 46.0°C, control arm median 55.0°C, difference between medians -9.0, 95% CI -11.8 to -6.2) They were significantly more likely to be happy or very happy with their bath hot water temperature (RR 1.43, 95% CI 1.05 to 1.93), significantly less likely to report the temperature as being too hot (RR 0.33, 95% CI 0.16 to 0.68) and significantly less likely to report checking the temperature of every bath (RR 0.84, 95% CI 0.73 to 0.97). Seven (15%) intervention arm families reported problems with their TMV. CONCLUSIONS: TMVs and accompanying educational leaflets are effective at reducing bath hot tap water temperatures in the short and longer term and are acceptable to families. Housing providers should consider fitting TMVs in their properties and legislators should consider mandating their use in refurbishments as well as in new builds.

Parental poison prevention practices and their relationship with perceived toxicity: cross-sectional study.

OBJECTIVE: To describe poison prevention practices for a range of substances and explore the relationship between prevention practices and perceptions of toxicity. DESIGN: Cross-sectional study using a validated postal questionnaire. PARTICIPANTS: Parents with children aged 12-35 months on 23 health visitors' caseloads. SETTING: Areas of various levels of deprivation in Nottingham, UK. MAIN OUTCOME MEASURES: Possession and storage of substances, putting substances away immediately after use, and perceptions of toxicity. RESULTS: Dishwasher tablets (68%), toilet cleaner (71%), bleach (74%), oven cleaner (78%), oral contraceptives (80%), and essential oils (81%) were least likely to be stored safely. Children's painkillers (69%), cough medicine (72%), and essential oils (77%) were least likely to be put away immediately after use. More than 50% of parents perceived antibiotics and oral contraceptives as harmful in small quantities and cough medicines as harmful only in large quantities. Six substances perceived by parents to be more harmful were more likely to be put away immediately after use. Parents perceiving dishwasher tablets (OR 1.96, 95% CI 1.05 to 3.66), essential oils (OR 2.80, 95% CI 1.35 to 5.81), turpentine (OR 14.54, 95% CI 2.75 to 76.95), and rat/ant killer (OR 15.33, 95% CI 2.01 to 116.82) as more harmful were more likely to store these substances safely. CONCLUSIONS: Parents' perceptions of toxicity of substances were sometimes inaccurate. Perceived toxicity was associated with putting substances away immediately after use for six substances and with safe storage for four substances. The effect of addressing perceptions of toxicity on poison prevention practices requires evaluation.

Validating parents' self-reports of children's exposure to potentially toxic substances within the home.

OBJECTIVE: To validate self-reported possession and storage of a range of substances within the home. PARTICIPANTS: 30 families with children aged 12-35 months on health visitor caseloads in Nottingham, UK. METHODS: Self-reported possession and storage of potentially hazardous substances were validated by observations. Sensitivity, specificity, and predictive values were calculated for possession, storage, and exposure to substances. RESULTS: Self-reported low exposure to substances had high sensitivities (87-100%) and positive predictive values (75-100%) for all substances, except toilet cleaner (positive predictive value 62%) and high negative predictive values for commonly owned household products. Specificity and negative predictive value could not be estimated reliably for medicines and less commonly owned household products, as few families stored these unsafely. CONCLUSIONS: A measurement of exposure that combines self-reported possession and storage may be sufficiently accurate to identify families with safer poison prevention practices.

Inequalities in hospital admission rates for unintentional poisoning in young children.

OBJECTIVE: To determine the relationship between deprivation and hospital admission rates for unintentional poisoning, by poisoning agent in children aged 0-4 years. DESIGN: Cross sectional study of routinely collected hospital admissions data. SETTING: East Midlands, UK. PARTICIPANTS: 1469 admissions due to unintentional poisoning over two years. MAIN OUTCOME MEASURE: Hospital admission rates for unintentional poisoning. Incidence rate ratios (IRRs) comparing hospital admission rates for poisoning in the most and least deprived electoral wards. RESULTS: Children in the most deprived wards had admission rates for medicinal poisoning that were 2-3 times higher than those in the least deprived wards (IRR 2.49, 95% CI 1.87 to 3.30). Admission rates for non-medicinal poisoning were about twice as high in the most compared to the least deprived wards (IRR 1.77, 95% CI 1.19 to 2.64). Deprivation gradients were particularly steep for benzodiazepines (IRR 5.63, 95% CI 1.72 to 18.40), antidepressants (IRR 4.58, 95% CI 1.80 to 11.66), cough and cold remedies (IRR 3.93, 95% CI 1.67 to 9.24), and organic solvents (IRR 3.69, 95% CI 1.83 to 7.44). CONCLUSIONS: There are steep deprivation gradients for admissions to hospital for childhood poisoning, with particularly steep gradients for some psychotropic medicines. Interventions to reduce these inequalities should be directed towards areas of greater deprivation.

Do rates of hospital admission for falls and hip fracture in elderly people vary by socio-economic status?

OBJECTIVE: To determine the relationship between hospital admissions for falls and hip fracture in elderly people and area characteristics such as socio-economic deprivation. STUDY DESIGN: Ecological study of routinely collected hospital admissions data for falls and hip fracture in people aged 75 years or over for 1992-1997, linked at electoral ward level with characteristics from census data. METHODS: In total, 42,293 and 17,390 admissions were identified for falls and hip fracture, respectively, from 858 electoral wards in Trent. Rate ratios (RRs) for hospital admissions for falls and hip fracture were calculated by the electoral wards' Townsend score divided by quintiles. RRs were estimated by negative binomial regression and adjusted for the ward characteristics of age, gender, ethnicity, rurality, proportion of elderly people living alone and distance from hospital. RESULTS: There was a small but statistically significant association at electoral ward level between hospital admissions for falls and the Townsend score, with the most deprived wards having a 10% higher admission rate for falls compared with the most affluent wards (adjusted RR 1.10, 95% CI 1.01-1.19). No association was found between hospital admission for hip fracture and deprivation (adjusted RR 1.05, 95% CI 0.95-1.16). CONCLUSION: There is some evidence of an association at electoral ward level between hospital admissions for falls and socio-economic deprivation, with higher rates in deprived areas. No such association was found for hip fracture. Further work is required to assess the impact of interventions on reducing inequalities in hospital admission rates for falls in elderly people.

Randomised controlled trial of an occupational therapy intervention to increase outdoor mobility after stroke.

OBJECTIVE: To evaluate an occupational therapy intervention to improve outdoor mobility after stroke. DESIGN: Randomised controlled trial. SETTING: General practice registers, social services departments, a primary care rehabilitation service, and a geriatric day hospital. PARTICIPANTS: 168 community dwelling people with a clinical diagnosis of stroke in previous 36 months: 86 were allocated to the intervention group and 82 to the control group. INTERVENTIONS: Leaflets describing local transport services for disabled people (control group) and leaflets with assessment and up to seven intervention sessions by an occupational therapist (intervention group). MAIN OUTCOME MEASURES: Responses to postal questionnaires at four and 10 months: primary outcome measure was response to whether participant got out of the house as much as he or she would like, and secondary outcome measures were response to how many journeys outdoors had been made in the past month and scores on the Nottingham extended activities of daily living scale, Nottingham leisure questionnaire, and general health questionnaire. RESULTS: Participants in the treatment group were more likely to get out of the house as often as they wanted at both four months (relative risk 1.72, 95% confidence interval 1.25 to 2.37) and 10 months (1.74, 1.24 to 2.44). The treatment group reported more journeys outdoors in the month before assessment at both four months (median 37 in intervention group, 14 in control group: P < 0.01) and 10 months (median 42 in intervention group, 14 in control group: P < 0.01). At four months the mobility scores on the Nottingham extended activities of daily living scale were significantly higher in the intervention group, but there were no significant differences in the other secondary outcomes. No significant differences were observed in these measures at 10 months. CONCLUSION: A targeted occupational therapy intervention at home increases outdoor mobility in people after stroke.

Ca2+ release through ryanodine receptors regulates skeletal muscle L-type Ca2+ channel expression.

Skeletal muscle obtained from mice that lack the type 1 ryanodine receptor (RyR-1), termed dyspedic mice, exhibit a 2-fold reduction in the number of dihydropyridine binding sites (DHPRs) compared with skeletal muscle obtained from wild-type mice (Buck, E. D., Nguyen, H. T., Pessah, I. N., and Allen, P. D. (1997) J. Biol. Chem. 272, 7360-7367 and Fleig, A., Takeshima, H., and Penner, R. (1996) J. Physiol. (Lond.) 496, 339-345). To probe the role of RyR-1 in influencing L-type Ca(2+) channel (L-channel) expression, we have monitored functional L-channel expression in the sarcolemma using the whole-cell patch clamp technique in normal, dyspedic, and RyR-1-expressing dyspedic myotubes. Our results indicate that dyspedic myotubes exhibit a 45% reduction in maximum immobilization-resistant charge movement (Q(max)) and a 90% reduction in peak Ca(2+) current density. Calcium current density was significantly increased in dyspedic myotubes 3 days after injection of cDNA encoding either wild-type RyR-1 or E4032A, a mutant RyR-1 that is unable to restore robust voltage-activated release of Ca(2+) from the sarcoplasmic reticulum (SR) following expression in dyspedic myotubes (O'Brien, J. J., Allen, P. D., Beam, K., and Chen, S. R. W. (1999) Biophys. J. 76, A302 (abstr.)). The increase in L-current density 3 days after expression of either RyR-1 or E4032A occurred in the absence of a change in Q(max). However, Q(max) was increased 85% 6 days after injection of dyspedic myotubes with cDNA encoding the wild-type RyR-1 but not E4032A. Because normal and dyspedic myotubes exhibited a similar density of T-type Ca(2+) current (T-current), the presence of RyR-1 does not appear to cause a general overall increase in protein synthesis. Thus, long-term expression of L-channels in skeletal myotubes is promoted by Ca(2+) released through RyRs occurring either spontaneously or during excitation-contraction coupling.

Variations in GP nursing home patient workload: results of a multivariate analysis.

The number of old people living in UK nursing homes has increased substantially over the past 15 y. There is evidence that such patients generate larger workloads for primary carers than do those of similar age and sex living in their own homes. Clearly, any extra workload involved in providing primary care services to nursing home patients, needs to be reflected in the resources afforded general practitioners (GPs) who are tasked with its provision. By the same token variations in workloads between patients need to be examined and explained for any insights these might provide on funding issues. To examine and explain variations in GP workload associated with nursing home patients and determine the implications of these for GP funding, a 12 month case control study of all nursing home residents over 65 y old registered with nine general practices was undertaken. A multivariate regression analysis was used to examine variations in GP workload associated with 270 nursing home patients. Multivariate regression models explaining the variation in workload cost per month in terms of the GP practice delivering care and patients age and sex had little explanatory power (R(2)=0.07). A fuller method including the patient's Barthel score and initial diagnosis as additional explanatory variables added little to the explanatory power of the model (R(2)=0.12). The ability of the multivariate models used here to explain the variation in GP workload was poor. GPs may require an allowance to compensate for differences in workload associated with nursing home patients but adjusting these payments for differences in age, sex, initial diagnosis or the other variables included in this analysis would not appear to be supported.

Is there a role for computerized decision support for drug dosing in general practice? A questionnaire survey.

OBJECTIVE: To determine: (i) whether general practitioners have difficulty with drug dosing; (ii) what information sources they currently use to help them with drug dosing; (iii) their views on the potential value of decision support software for drug dosing. DESIGN: Questionnaire survey. SETTING: Nottingham, U.K. PARTICIPANTS: 263 general practitioners (GPs). RESULTS: The response rate was 78% (263/336). Most GPs reported difficulties with drug dosing for children, the elderly and patients with renal impairment. Compared with 'patients in general', GPs had particular difficulties in drug dosing for these specific groups (P < 0.001). Paper-based formularies were the most common source of information for help with drug doses. Nevertheless, most GPs had positive views on the potential usefulness of computerized decision support. CONCLUSION: GPs commonly have problems in drug dosing for certain groups of patients. The development and use of computerized decision support might help GPs in these situations.

The impact of nursing home patients on general practitioners' workload.

BACKGROUND: Although the number of people in nursing homes has risen substantially in recent years, the shift of responsibility into general practice has rarely been accompanied by extra resources. These patients may be associated with a higher general practitioner (GP) workload than others of similar age and sex. AIM: To assess the GP workload associated with nursing home residents and its associated costs. METHOD: All nursing home residents aged over 65 years and registered with nine Nottinghamshire practices during one year were matched with patients living in the community for general practice, age, and sex. Data were collected retrospectively for both groups on key workload measures. Costs for the workload measures were calculated using published estimates. RESULTS: Data were collected for 270 pairs of patients. Nursing home patients had more face-to-face contacts in normal surgery hours, telephone calls, and out-of-hours visits. The mean workload cost per month of a nursing home patient (assuming that one patient was seen per visit) was estimated to be 18.21 Pounds (10.49 Pounds higher than the cost of controls). A sensitivity analysis demonstrated that potential savings in visiting costs associated with increasing the numbers of patients seen per visit were 27% for one extra patient seen per visit and 44% for four extra patients. CONCLUSION: Nursing home residents were associated with higher workload for GPs than other patients of the same age and sex living in the community. Our costings provide a basis for negotiating suitable reimbursement of GPs for their additional work.

Arthrodesis of the proximal interphalangeal joint affected with septic arthritis in 8 horses.

Arthrodesis was performed to treat septic arthritis of the proximal interphalangeal joint of 8 horses. Records of the horses were reviewed to determine outcome and possible factors that influenced success or failure. All horses were female. Seven horses had 1 joint treated and 1 horse was treated for bilateral pelvic limb involvement. The duration of sepsis before surgery ranged from 1 to 66 days. Bone lysis and production was radiographically apparent in 7 horses before surgery. Six horses had multiple bacterial organisms cultured from bone or synovial tissues; 2 horses had single isolates identified. After aggressive curettage, arthrodesis was accomplished with 3 parallel screws in 1 horse, 2 divergent narrow dynamic compression plates in 3 horses, and a single broad dynamic compression plate in 4 horses. Casts were applied to all horses for 1 to 6 weeks. Four horses survived to successful brood mare status. Four horses were euthanized during hospitalization because of continued discomfort or complications of sepsis. Arthrodesis of the proximal interphalangeal joint affected with septic arthritis appears to be an acceptable alternative to euthanasia for some horses.

Age and proximity to death as predictors of GP care costs: results from a study of nursing home patients.

This paper reports the results of a study of GP costs associated with a group of nursing home patients who died at various stages during a 12-month period. The relationship between costs per month of care, patient age and proximity to death, where sex and diagnosis are controlled for are reported. A comparison of care costs for patients in their last year of life and those who survived the course of the study is also made. The study found that those in their last year of life were significantly more expensive to care for than those who survived the duration of the study, but that there was no statistically significant difference in age. In multivariate regression analyses, it was also found that among those who died during the study care costs were unrelated to age, but significantly related to proximity to death. The study supports the contention of others (Zweifel P, Felder S, Meiers M. Ageing of population and health care expenditure: a red herring? Health Econ 1999; 8: 485-496) that health care costs are more directly related to proximity to death than age.

The impact of nursing home patients on prescribing costs in general practice.

OBJECTIVES: To compare the costs of prescribing for older people in nursing homes with older people living at home and to compare patterns of prescribing between these two groups. DESIGN: Retrospective case-control study. SETTING: Nine general practices in Nottinghamshire. SUBJECTS: Two hundred and seventy patients aged 65 years and over living in nursing homes matched for age, sex and general practice, with 270 patients living in their own homes. MAIN OUTCOME MEASURES: A comparison of the costs of prescriptions, the number of items on prescription and the types of drugs prescribed between the cases and controls. RESULTS: The mean cost of prescriptions per patient month was almost three times higher for nursing home patients than controls (45.27 pounds compared to 16.46 pounds). The mean number of items prescribed per patient month was also higher in nursing home patients (5.60 compared to 2.55). Total costs of prescriptions for nursing home patients were higher than for controls (P < 0.0001), as were total numbers of prescription items (P < 0.001). There were differences in the types of medication prescribed between the two groups, including considerably higher costs for central nervous system drugs, ulcer healing drugs, laxatives and enteral nutrition in nursing home residents. CONCLUSIONS: When calculating general practice prescribing budgets, nursing home patients should have a greater weighting than other patients of similar age and sex.

What problems do patients present with outside normal general practice surgery hours? A prospective study of the use of general practice and accident and emergency services.

BACKGROUND: This study was designed to address some current issues concerning the use of general practice and accident and emergency (A & E) services outside normal surgery hours. METHOD: Six general practices in Nottingham (with a combined population of 46,698 patients) were recruited to take part in the study. Over a six month period, data were collected on patient contacts with general practice services and the local A & E department outside normal surgery hours. RESULTS: General practice services dealt with 63 per cent of first contacts over the course of the study. There were 3181 (136 per 1000 patients per year) contacts with general practitioners and deputizing service doctors (of which 1009 (31.7 per cent) were dealt with by telephone alone) and 1876 (80 per 1000 patients per year) attendances at the A & E department. There were marked differences in the distribution of problems that patients presented to the two types of service. The proportion of presentations dealt with by telephone alone by general practice services varied with the type of presentation. However, the use of the telephone was not particularly high, even for problems such as a sore throat. CONCLUSIONS: Given the differences in presentations to both general practice and A & E services there may be limited scope for altering patients' consulting patterns without making significant changes to service provision. However, there may be scope for increasing the proportion of general practice contacts dealt with by telephone alone.

Explaining variations in prescribing costs: results from a comparison of nursing home patients with matched pairs living in the community.

OBJECTIVES: To examine and explain variations in prescribing costs associated with nursing home patients and patients matched by age and sex living in the community. DESIGN: A 12-month case control study. SUBJECTS: All nursing home residents over 65-years-old registered with nine general practices and patients matched with them for age and sex living in the community. METHOD: Multivariate regression analysis of variations in monthly GP prescribing costs. RESULTS: Multivariate regression models explaining cost variations in terms of the GP practice delivering care and patients' age and sex had little explanatory power (R(2)=0.07 for nursing home patients, R(2)=0.03 for matched pairs). A fuller model for nursing home patients only, incorporating the patient's Barthel score and initial diagnosis as additional explanatory variables, added little to the explanatory power of the model (R(2)=0.16). CONCLUSION: The ability of the multivariate models used here to explain variations in prescribing costs among a group of elderly patients is poor. Adjusting weighted capitation formulae with respect to older patients to take account of such information or referring to it in negotiations on prescribing budgets would not appear to be warranted.

Relation of out of hours activity by general practice and accident and emergency services with deprivation in Nottingham: longitudinal survey.

OBJECTIVES: To investigate the relation between out of hours activity of general practice and accident and emergency services with deprivation and distance from accident and emergency department. DESIGN: Six month longitudinal study. SETTING: Six general practices and the sole accident and emergency department in Nottingham. SUBJECTS: 4745 out of hours contacts generated by 45,182 patients from 23 electoral wards registered with six practices. MAIN OUTCOME MEASURES: Rates of out of hours contacts for general practice and accident and emergency services calculated by electoral ward; Jarman and Townsend deprivation scores and distance from accident and emergency department of electoral wards. RESULTS: Distances of wards from accident and emergency department ranged from 0.8 to 9 km, and Jarman deprivation scores ranged from -23.4 to 51.8. Out of hours contacts varied by ward from 110 to 350 events/1000 patients/year, and 58% of this variation was explained by the Jarman score. General practice and accident and emergency rates were positively correlated (Pearson coefficient 0.50, P = 0.015). Proximity to accident and emergency department was not significantly associated with increased activity when deprivation was included in regression analysis. One practice had substantially higher out of hours activity (B coefficient 124 (95% confidence interval 67 to 181)) even when deprivation was included in regression analysis. CONCLUSIONS: A disproportionate amount of out of hours workload fell on deprived inner city practices. High general practice and high accident and emergency activity occurred in the same areas rather than one service substituting for the other.

Changes in the role of general practitioners in child health surveillance.

BACKGROUND: Changes in their Contract in 1990 gave general practitioners the opportunity to become more involved in child health surveillance. This study aimed to describe and compare child health surveillance services provided by general practitioners before and after the changes of the 1990 GP contract. METHODS: A questionnaire was sent to all general practices within the Nottingham Health Authority area in 1990, and this process was repeated in 1994, ascertaining the services provided for child health surveillance. Outcome measures were: the reported provision of services, keeping of records and facilities for following up non-attenders. Also recorded were the training and qualifications of general practitioners and their attitudes towards child health surveillance. RESULTS: Response rates were 62% in 1990 and 80% in 1994. More practices were involved in the provision of child health surveillance services in 1994, more held a baby clinic and more reported having a recall system for non-attenders. There was little change in the training or qualifications of GPs in child health between 1990 and 1994. In 1994, there was evidence of GPs meeting regularly with Health Visitors. There remained a small number of practices who were not interested in child health surveillance. CONCLUSION: The 1990 GP contract appears to have increased the provision of child health surveillance services by GPs and improved liaison with Health Visitors in general practice.

Problems found in the over-75s by the annual health check.

BACKGROUND: Research into the health of elderly people has found problems unknown to their general practitioners. It was anticipated that annual checks, as required by the 1990 general practitioner contract, would help to detect these problems, yet the value of these checks has been questioned. AIM: To investigate the problems found by general practice contractual annual checks of the over-75s and the consequent actions taken; to identify patient, demographic or practice characteristics associated with the discovery of problems. METHOD: In 40 practices, information was collected on patients over 75 years of age receiving a health check during a 3-month period. Practices used their normal methods of recruitment and assessment. Practice staff were interviewed to find how assessments were organized. RESULTS: Practices saw a mean of 12% of their over-75s during the study; 44% were found to have at least one problem. Action was taken to help resolve problems in 82% of patients with a problem. The most prevalent problems related to physical condition, and fewer functional problems than expected were found. There were large differences between practices in the proportions of elderly patients seen for a check and the proportion found to have problems; these were not attributable to practice size or demography. Multivariate analysis showed that practice or patient characteristics were poor predictors of finding problems. CONCLUSION: The argument in favour of conducting annual checks is supported by the finding that nearly half the patients assessed were found to have problems for which some action was taken. Some practices could increase their rate of uptake by modifying the organization of invitations for checks. More problems may be found by adopting a more functionally based assessment.

Differential regulation of the MAP, SAP and RK/p38 kinases by Pyst1, a novel cytosolic dual-specificity phosphatase.

The Pyst1 and Pyst2 mRNAs encode closely related proteins, which are novel members of a family of dual-specificity MAP kinase phosphatases typified by CL100/MKP-1. Pyst1 is expressed constitutively in human skin fibroblasts and, in contrast to other members of this family of enzymes, its mRNA is not inducible by either stress or mitogens. Furthermore, unlike the nuclear CL100 protein, Pyst1 is localized in the cytoplasm of transfected Cos-1 cells. Like CL100/ MKP-1, Pyst1 dephosphorylates and inactivates MAP kinase in vitro and in vivo. In addition, Pyst1 is able to form a physical complex with endogenous MAP kinase in Cos-1 cells. However, unlike CL100, Pyst1 displays very low activity towards the stress-activated protein kinases (SAPKs) or RK/p38 in vitro, indicating that these kinases are not physiological substrates for Pyst1. This specificity is underlined by the inability of Pyst1 to block either the stress-mediated activation of the JNK-1 SAP kinase or RK/p38 in vivo, or to inhibit nuclear signalling events mediated by the SAP kinases in response to UV radiation. Our results provide the first evidence that the members of the MAP kinase family of enzymes are differentially regulated by dual-specificity phosphatases and also indicate that the MAP kinases may be regulated by different members of this family of enzymes depending on their subcellular location.

XCL100, an inducible nuclear MAP kinase phosphatase from Xenopus laevis: its role in MAP kinase inactivation in differentiated cells and its expression during early development.

We have cloned the Xenopus laevis homologue (XCL100) of the human CL100 (Thr/Tyr) MAP kinase phosphatase. Expression of the XCL100 mRNA and protein is inducible by serum stimulation and oxidative/heat stress in a X. laevis kidney cell line. In contrast, XCL100 is constitutively expressed in growing Xenopus oocytes. Recombinant XCL100 protein is able to dephosphorylate both tyrosine and threonine residues of activated p42 MAP kinase in vitro and both the Xenopus and human CL100 proteins were localised predominantly in the nucleus in transfected COS-1 cells. As nuclear translocation of activated MAP kinase is necessary for some of its essential functions in proliferation and cell differentiation our results indicate a role for CL100 in the regulation of these nuclear signalling events. In Xenopus kidney cells both heat shock and serum stimulation lead to transient activation of MAP kinase. However, in contrast to results previously reported from studies on mammalian fibroblasts the inactivation of MAP kinase in these epitheloid cells is rapid and is not dependent on synthesis of new protein. These results indicate that the induction of CL100 (or CL100-like enzymes) may not be required for MAP kinase inactivation in all cell types. Finally, during early embryogenesis, levels of XCL100 mRNA are greatly increased at the mid-blastula transition, suggesting that this enzyme may be involved in the regulation of MAP kinase activity during early development.