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Biomedical subjects

B A Mueller

Publications and source records attributed to B A Mueller.

At least 55 records · Page 3Linked to original sources
PubMed1998

Farm and animal exposures and pediatric brain tumors: results from the United States West Coast Childhood Brain Tumor Study.

Nineteen counties from San Francisco and Los Angeles, California and Seattle, Washington were the United States sites for a large population-based case-control study of childhood brain tumors (CBTs), sponsored by the National Cancer Institute. CBT patients who were < 20 years of age and were diagnosed between 1984 and 1991 were reported to each region's cancer registry. The 801 control subjects were obtained by random digit dial and were frequency-matched to the 540 CBT patients in San Francisco and Seattle (one patient to two controls) and in Los Angeles (one patient to one control). Data collected by in-person interview with subjects' mothers were analyzed to investigate an association between risk for CBTs and life on a farm, exposure to farm animals (dairy cattle, beef cattle, pigs, sheep/goats, poultry, and horses), and some cat and non-farm horse exposures. Elevated risks for CBTs were observed in association with mothers' exposure to pigs [odds ratio (OR) = 3.8, 95% confidence interval (CI) = 1.2-12] and horses (OR = 2.2, 95% CI = 1.0-4.8) on a farm during the index pregnancy. Children diagnosed with primitive neuroectodermal tumors showed elevated risks for CBTs with personal and maternal prenatal exposure to pigs (child, OR = 4.0, 95% CI = 1.2-13; mother, OR = 11.9, 95% CI = 2.8-51) and poultry (child, OR = 3.0, 95% CI = 1.1-8.0; mother, OR = 4.0, 95% CI = 1.2-14). No other animal exposures of children or mothers were found to be consistently related to CBTs. Children diagnosed with primitive neuroectodermal tumors who were on a farm for > 1 year and were first on a farm when they were < 6 months of age also had increased risk for CBTs (OR = 3.9, 95% CI = 1.2-13). A somewhat increased risk for CBTs was found for children of mothers who ever had worked on livestock farms compared with mothers who never had worked on a farm (OR = 7.4, 95% CI = 0.86-64, based on five case mothers and one control mother who worked on livestock farms during the 5 years preceding the birth of the index child). The associations are consistent with those of two previous studies in Norway (P. Kristensen et al., Int. J. Cancer, 65: 39-50, 1996) and the United States and Canada (G. R. Bunin et al., Cancer Epidemiol. Biomark. Prev., 3: 197-204, 1994) that investigated the role of farm-related exposures in the etiology of CBTs.

Adolescent↗
PubMed1998

Prenatal vitamin supplementation and risk of childhood brain tumors.

An international case-control study of primary pediatric brain tumors included interviews with mothers of cases diagnosed from 1976 to 1994 and mothers of population controls. Data are available on maternal vitamin use during pregnancy for 1,051 cases and for 1,919 controls from 8 geographic areas in North America, Europe and Israel. While risk estimates varied by study center, combined results suggest that maternal supplementation for 2 trimesters decreased risk of brain tumor [odds ratio (OR) = 0.7; 95% confidence interval (CI) = 0.5, 0.9], with a trend of less risk with longer duration of use (p trend = 0.0007). The greatest risk reduction was among children diagnosed under 5 years of age whose mothers used supplements during all 3 trimesters (OR = 0.5; CI = 0.3, 0.8). This effect did not vary by histology and was seen for supplementation during pregnancy rather than during the month before pregnancy or while breastfeeding. Our findings are largely driven by data from the United States, where most mothers took vitamins. The proportion of control mothers who took vitamins during pregnancy varied markedly from 3% in Israel and in France, 21% in Italy, 33% in Canada and 52% in Spain to 86-92% at the 3 U.S. centers. The composition of the various multivitamin compounds taken also varied: daily dose of vitamin C ranged from 0 to 600 mg; vitamin E from 0 to 70 mg; vitamin A from 0 to 30,000 IU; and folate from 0 to 2,000 micrograms. Mothers also took individual micronutrient supplements (e.g., vitamin C tablets), but most mothers who took these also took multivitamins, making it impossible to determine the potential independent effects of these micronutrients.

Adolescent↗
PubMed1997

Alcohol and illicit drug abuse and the risk of violent death in the home.

CONTEXT: While acute alcohol and illicit drug use are common in homicide and suicide victims, the role of chronic substance use in violent death is unclear. OBJECTIVE: To measure the magnitude of risk of violent death in the home associated with alcohol use or chronic abuse and use of illicit drugs. DATA SOURCES: Data obtained from a case-control study of risk factors for homicide and suicide in 3 large metropolitan areas of the United States. DESIGN: Matched case-control study including 388 homicide cases, 438 suicide cases, and equal numbers of controls matched for age, sex, race, neighborhood, and county. Data were analyzed by means of conditional logistic regressions in which other potential risk factors for violent death were also considered. OUTCOME AND EXPOSURE MEASURES: Homicide and suicide victims were identified from medical examiner reports in Shelby County, Tennessee; King County, Washington; and Cuyahoga County, Ohio. Structured interviews were conducted with proxy respondents close to the decedents to obtain information about alcohol or illicit drug use, and history of alcohol-related hospitalization or trouble at work because of drinking by the subject. Data about alcohol use by others living in the same house as the subject were also obtained. RESULTS: The risks of homicide and suicide associated with alcohol or illicit drug use were elevated, as were the risks of violent death associated with several indicators of chronic alcohol abuse. In addition, nondrinkers living in a home with alcohol users were at increased risk of homicide (odds ratio, 1.7; 95% confidence interval, 0.98-3.0), and non-drug-using individuals residing in homes with illicit drug users were at greatly increased risk of homicide (odds ratio, 11.3; 95% confidence interval, 4.4-28.8). CONCLUSIONS: Alcohol and illicit drug use appear to be associated with an increased risk of violent death. The risk of homicide was increased for non-substance-abusing individuals living in households in which other members abused alcohol or drugs. The concept of the individual at risk of homicide should be broadened to include not only the abuser but also those who may be at risk because of their exposure to others.

Adolescent↗
PubMed1997

The role of renal replacement therapy quantification in acute renal failure.

The recognition that both morbidity and mortality are inversely related to delivered hemodialysis (HD) dose in end-stage renal disease (ESRD) patients has substantially changed clinical practices in the United States. A number of quantification techniques, which differ greatly in complexity and sophistication, are now used in ESRD patients. Investigators recently have attempted to extrapolate some of these ESRD quantification methods to the acute renal failure (ARF) setting. This review focuses on these recent attempts. Both patient-related and renal replacement therapy (RRT)-related differences in ESRD and ARF are discussed. In addition, the potential pitfalls of extrapolating certain ESRD quantification methods to RRT in ARF are discussed. Prescription considerations for both intermittent HD (IHD) and continuous RRT (CRRT) are presented. The optimal technique for RRT quantification in ARF remains to be determined.

Humans↗
PubMed1997

Data linkage methods used in maternally-linked birth and infant death surveillance data sets from the United States (Georgia, Missouri, Utah and Washington State), Israel, Norway, Scotland and Western Australia.

In this paper we describe the methods used to link birth and infant mortality and morbidity surveillance data sets into sibships using deterministic or multistage probabilistic linkage methods. We describe nine linked data sets: four in the United States (Georgia, Missouri, Utah and Washington State), and four elsewhere (Scotland, Norway, Israel and Western Australia). Norway and Israel use deterministic methods to link births and deaths into sibships. The deterministic linkage is usually dependent on the availability of national identification numbers. In both countries they assign these numbers at birth. Deterministic linkage is usually highly successful, and the major problem is the validation of linkages. In the United States, Western Australia and UK linkage is multistage and probabilistic. This approach is usually dependent on the calculation linkage weights from sociodemographic variables. The success rates of probabilistic methods are above 80%. Maternally-linked perinatal data open new vistas for epidemiological research. Recurrence of poor perinatal outcomes is more appropriately studied using longitudinally-linked data sets. In addition, the emergence of risk factors and the recurrence of risk factors can be studied.

Epidemiologic Methods↗
PubMed1997

Risk factors for the recurrence of premature rupture of the membranes.

Premature rupture of the amniotic membranes (PROM) occurs in up to 20% of all births. Although many studies have examined risk factors for PROM and, in particular, preterm PROM (PPROM, if less than 37 weeks' gestation), the aetiology of PROM recurrence has not been examined as closely. This study investigated factors that may increase the risk of PROM among women who have already experienced one PROM birth. Maternally linked Washington State birth certificates from 1984 to 1993 identified 208 women with consecutive PROM births. Controls were a random sample (n = 848) of women who had one birth on record complicated by PROM, but whose subsequent birth was not. Among women with a prior term PROM, increased risk for PROM recurrence (term PROM or PPROM) was associated with an intervening fetal death at less than 20 weeks' gestation (OR = 2.4, 1.3-4.5) and with parity of two or more (OR = 2.0, 1.3-3.4). None of the factors assessed significantly increased the risk of recurrence of PROM (term PROM or PPROM) among women with a prior PPROM. Other potential risk factors for PROM recurrence were evaluated within the two PROM groups (PPROM or term PROM at first birth) by stratifying among the cases according to gestational length at subsequent birth.

Case-Control Studies↗
PubMed1997

Risk of recurrence of birth defects in Washington State.

A population-based study was conducted using maternally-linked birth certificate records from Washington State for 1980-93 to evaluate the risk of birth defect occurrence among infants with previously affected siblings, relative to infants whose siblings did not have birth defects. The risks of recurrence of similar and dissimilar defects were estimated, and the effects of change in paternity and/or city of residence were evaluated as proxies of genetic and environmental effects. At the first birth on record, 3322 women were identified in the linked certificates as giving birth to a child with a birth defect; 6620 women whose first birth did not result in an infant with a defect were randomly selected for comparison. Women with a malformed infant had an increased risk of having a malformed infant at the subsequent birth (Relative Risk = 1.9, [95% Confidence Interval (CI) = 1.5-2.4]), which did not vary by intervening changes in partner or residence. The risk of recurrence of the same general type of defect [RR = 11.7, 95% CI = 9.7-19.50] was much greater than that of occurrence of a dissimilar defect [RR = 1.5, 95% CI = 1.1-1.9]. This was consistent for all defect categories, and did not vary markedly by changes in partner or residence.

Birth Order↗
PubMed1997

The association of change in maternal marital status between births and adverse pregnancy outcomes in the second birth.

The relationships between change in marital status between two consecutive births and adverse pregnancy outcomes at the second birth were investigated using linked Washington State 1980-93 white singleton birth certificates. Women who were married at the first birth had lower low birthweight (LBW) and small-size-for-gestational-age (SGA) rates at that birth than single women, and women married at the second birth had lower LBW, SGA and preterm delivery rates at that birth regardless of marital status at the first birth. Adjusted relative risks (RR) of LBW and SGA were significantly increased for initially married women who were single at the second birth compared with those who remained married (RR = 1.4 and 1.3, respectively). Risks of LBW and SGA were significantly decreased among initially single women who married by the second birth, compared with those remaining single (RR = 0.7 for LBW and 0.8 for SGA). We conclude that the largely unstudied subgroup of previously married women is at increased risk for adverse pregnancy outcomes. Public health policy and programmes directed at high-risk mothers and infants should be aware of the specific physical and emotional needs of this group of child-bearing women.

Adult↗
PubMed1997

Attempt and success rates for vaginal birth after caesarean section in relation to complications of the previous pregnancy.

The relationships between prior obstetrical complications and subsequent trial of labour and vaginal birth after Caesarean (VBAC) success likelihood were examined among a cohort of Washington State women with a first livebirth via Caesarean delivery and a second livebirth between 1987 and 1993 (n = 10110). Overall, 64% of the cohort undertook a labour trial, and 62% of those who attempted VBAC delivery were successful, for an overall VBAC rate of 40%. Women with fetal macrosomia, cephalopelvic disproportion, prolonged labour, diabetes, or placental problems in the first pregnancy were less likely to undergo a labour trial in the second pregnancy than those without these factors, while women with prior induced labour, genital herpes, fetal distress, or breech presentation were more likely to attempt vaginal birth. Approximately half of women with prior macrosomia, labour problems, or chronic medical conditions who attempted VBAC succeeded, as did three-quarters of women with prior breech presentation or placental conditions. Overall VBAC rates were around 33% for women with previous fetal macrosomia, labour problems, or chronic medical conditions, and 45-55% among those with herpes, fetal distress or breech presentation at the first birth. Trial of labour should especially be encouraged among women without prior labour problems.

Adult↗
PubMed1997

Vancomycin mass transfer characteristics of high-flux cellulosic dialysers.

BACKGROUND: In comparison to conventional haemodialysis membranes, highly permeable membranes allow a broader spectrum of solute removal, including enhanced elimination of vancomycin (1448 Daltons). However, the mass transfer characteristics of vancomycin removal by highly permeable membranes have not been adequately assessed. An understanding of vancomycin's predominant dialytic mass transfer mechanism under a given set of operating conditions, including dialyser type and flow rates, may permit more accurate dosing of the drug. METHODS: We performed a mass transfer analysis of vancomycin removal by a high-flux dialyser, cellulose triacetate (CT). In a cross-over fashion with a 3-week washout between treatments, eight subjects received vancomycin 1000 mg (1) during the last hour of CT haemodialysis; or (2) after dialysis. Serial urea and vancomycin serum concentrations were used to assess dialytic removal. RESULTS: Dialysis removed 26.2% (mean; range 16-44%) of the administered vancomycin dose. While vancomycin removal and (Kt/V)urea were directly correlated (r = 0.88; P < 0.005), no correlation was observed between vancomycin removal and weight-normalized ultrafiltration rate. CONCLUSIONS: These findings suggest that for the CT dialyser and dialysis operating conditions employed in this study, vancomycin clearance was primarily mediated by diffusion. As such, these data challenge the general concept that convection is primarily responsible for the removal of solutes in the same molecular weight class as vancomycin during high-flux dialysis.

Adult↗
PubMed1997

A study of pediatric brain tumors and their association with epilepsy and anticonvulsant use.

OBJECTIVES: To evaluate the risk of childhood brain tumor occurrence in relation to epilepsy and anticonvulsant use. STUDY DESIGN: As part of a multicenter case-control study of pediatric brain tumors, maternal report on epilepsy occurrence before diagnosis of her child's brain tumor was collected for 540 cases and compared with 801 control children. Mothers also reported on any long-term (> or = 2 weeks) use of medications by her child before the date of tumor diagnosis (or a comparable reference date for controls) and these medications were classified according to whether they contained barbiturates. RESULTS: As expected, because seizures are often an early brain tumor symptom, a strong association was observed between epilepsy and brain tumor occurrence (odds ratio, OR = 6.2; 95% confidence limit, CL = 2.9, 14). The association remained elevated even after a > or = 10-year interval between diagnoses of epilepsy and brain tumor (OR = 4.7; CL = 0.8, 48). Elevated odds ratios were observed both for epileptic children who were treated with anticonvulsants containing barbiturates (OR = 5.8; CL = 2.2, 18) and for those not treated with barbiturates (OR = 7.9; CL = 1.7, 74), relative to nonepileptic children. CONCLUSION: Whereas most of the brain tumor risk associated with epilepsy may be due to occult tumors, the finding of an elevated risk many years after diagnosis of epilepsy is of interest.

Adolescent↗
PubMed1997

Automated peritoneal dialysis: new implications for pharmacists.

OBJECTIVE: To review the new automated peritoneal dialysis (APD) modalities that are available to patients with end-stage renal disease (ESRD), and to examine their potential pharmacokinetic and drug dosing consequences. DATA SOURCES: A MEDLINE search (from January 1966 to June 1996) of English-language literature pertaining to peritoneal dialysis was performed. Additional references were obtained by reviewing the references of pertinent articles identified through the search. Tertiary sources were also used. DATA EXTRACTION: Data regarding peritoneal dialysis techniques and pharmacokinetics were extracted from the literature. Data were evaluated according to the study design, population, results, and conclusions. DATA SYNTHESIS: ESRD is the result of progressive chronic renal insufficiency and requires renal replacement therapy. APD is the fastest growing renal replacement therapy by percentage in the US and provides dialysis exchanges via a machine while the patient sleeps, thereby improving patient convenience, peritoneal dialysis compliance rates, and decreasing peritonitis rates. Well-designed pharmacokinetic studies involving APD have not been conducted. Consequently, no formal drug dosing recommendations are available for APD, and pharmacists must rely on established dosing guidelines for continuous ambulatory peritoneal dialysis (CAPD) when recommending dosing regimens. This article describes the new APD treatment modalities available and the potential pharmacokinetic differences between CAPD and APD. CONCLUSIONS: Well-designed studies are needed to fully characterize the pharmacokinetic parameters of drugs in APD. Until then, pharmacists should recommend that intraperitoneally administered drugs be given during the longest peritoneal dialysate dwell of the day and that serum concentrations of drugs with narrow therapeutic indices be monitored closely.

Anti-Bacterial Agents↗
PubMed1997

Extracorporeal therapy requirements for patients with acute renal failure.

Renal replacement therapy (RRT) requirements for critically ill patients with acute renal failure (ARF) depend on numerous factors, including the degree of hypercatabolism, patient size, and desired level of metabolic control. However, the current practice at many institutions is to prescribe generally similar amounts of RRT to ARF patients essentially without regard for the above factors. In this study, a computer-based model designed to permit individualized RRT prescription to ARF patients was developed. The critical input parameter is the desired level of metabolic control, which is the time-averaged BUN (BUNa) or steady-state BUN (BUNs) for intermittent hemodialysis (IHD) or continuous RRT (CRRT), respectively. The basis for the model was a group of 20 patients who received uninterrupted CRRT for at least 5 days. In these patients, the normalized protein catabolic rate (nPCR) increased linearly (r = 0.974) from 1.55 +/- 0.14 g/kg per day (mean +/- SEM) on day 1 to 1.95 +/- 0.15 g/kg per day on day 6. The daily urea generation rate (G), determined from the above linear relationship, was utilized to produce BUN versus time curves by the direct quantification method for simulated patients of varying dry weights (50 to 100 kg) who received variable CRRT urea clearances (500 to 2000 ml/h). Steady-state BUN versus time profiles for the same simulated patient population treated with IHD regimens (K = 180 ml/min, T = 4 h) of variable frequency were generated by use of a variable-volume, single-pool kinetic model. From these profiles, regression lines of required IHD frequency (per week) versus patient weight for desired BUNa values of 60, 80, and 100 mg/dl were obtained. Regression lines of required CRRT urea K (ml/h) versus patient weight for desired BUNs values of 60, 80, and 100 mg/dl were also generated. For the attainment of intensive IHD metabolic control (BUNa = 60 mg/dl) at steady state, a required treatment frequency of 4.4 dialyses per week is predicted for a 50-kg patient. However, the model predicts that the same degree of metabolic control cannot be achieved even with daily IHD therapy in patients > or = 90 kg. On the other hand, for the attainment of intensive CRRT metabolic control (BUNs = 60 mg/dl), required urea clearance rates of approximately 900 ml/h and 1900 ml/h are predicted for 50- and 100-kg patients, respectively. This model suggests that, for many patients, rigorous azotemia control equivalent to that readily attainable with most CRRT can only be achieved with intensive IHD regimens. Following prospective clinical validation, this methodology may be a useful RRT prescription tool for critically ill ARF patients.

Acute Kidney Injury↗
PubMed1997

Ras oncogene mutations in childhood brain tumors.

Although N-nitroso compounds (NNC) are ubiquitous in the human environment and are known neurocarcinogens in animal models, results of epidemiological studies have not yet convincingly associated NNCs with brain tumor occurrence in humans. Animal studies have suggested that specific codons (12, 13, and 61) in the ras family are mutable by exposure to NNCs. The purpose of this study was to measure the presence of mutations in the ras family of oncogenes in tissue from childhood brain (CB) tumors as a preliminary step toward investigating their potential use as biomarkers of chemical exposure. DNA was extracted from paraffin-embedded formalin-fixed CB tumors from tissues resected during neurosurgical operations. Using the PCR, designed RFLP-screening methods, and sequencing, we attempted to screen brain tumors from 46 children for the presence of H, K, and N-ras mutations at codons 12, 13, and 61. Screening for oncogene mutations using PCR, RFLP methods, and DNA sequencing was successfully completed for a high proportion of the available specimens. Astrocytoma specimens from three children for whom screening with PCR was successfully completed were found to contain CAA-->GAA point mutations in K-ras at codon 61. None of the specimens contained mutations at any of the other locations. These results, although preliminary, provide a potential clue for future mechanistic studies of CB tumors. The possible roles of NNCs in inducing this mutation, or of this mutation as an early or late event in tumor progression, however, remain unclear.

Adolescent↗
PubMed1997

Dialysis prescription and kinetics in acute renal failure.

The recognition that both morbidity and mortality are inversely related to delivered hemodialysis (HD) dose in end-stage renal disease (ESRD) patients has substantially changed clinical practices in the United States. A number of quantification techniques, which differ greatly in complexity and sophistication, are now used in ESRD patients. Investigators recently have attempted to extrapolate some of these ESRD quantification methods to the acute renal failure (ARF) setting. This review focuses on these recent attempts. Both patient-related and renal replacement therapy (RRT)-related differences in ESRD and ARF are discussed. In addition, the potential pitfalls of extrapolating certain ESRD quantification methods to RRT in ARF are discussed. Prescription considerations for both intermittent HD (IHD) and continuous RRT (CRRT) are presented. Finally, recent data suggesting survival in critically ill ARF patients is directly correlated with delivered therapy dose are reviewed. The optimal technique for RRT quantification in ARF remains to be determined.

Acute Kidney Injury↗
PubMed1996

Uremic pruritus.

Uremic pruritus and its treatment are reviewed. Pruritus affects 50-90% of patients undergoing peritoneal dialysis or hemodialysis; symptoms usually begin about six months after the start of dialysis and range from localized and mild to generalized and severe. The mechanism underlying uremic pruritus is poorly understood; possibilities include secondary hyperparathyroidism and divalent-ion abnormalities; histamine, allergic sensitization, and proliferation of skin mast cells; hypervitaminosis A; iron-deficiency anemia; neuropathy and neurologic changes; or some combination of these. The cornerstone of therapy for uremic pruritus is regular, intensive, efficient dialysis. Other nonpharmacologic measures consist of the use of non-complement-activating dialysis membranes, compliance with dietary restrictions, electric-needle (acupuncture) therapy, and ultraviolet light therapy. Pharmacologic treatments that have been used include activated charcoal, antihistamines, capsaicin, cholestyramine, emollients and topical corticosteroids, epoetin, pizotyline, ketotifen, and nicergoline. Treatment results have been highly variable, and many of the clinical trials have been flawed. Phosphate-binding agents appear to be the most effective. Although enough is known to determine a reasonable set of steps in approaching a patient's uremic pruritus, more research is needed to understand the pathophysiology of this condition and to establish more reliable treatments. Pruritus is a common and sometimes severe complication of chronic renal failure. Efficient dialysis, dietary restrictions, phosphate-binding therapy, and phototherapy are the most effective treatments currently available.

Humans↗
PubMed1996

Lack of the DNA repair protein O6-methylguanine-DNA methyltransferase in histologically normal brain adjacent to primary human brain tumors.

Exposure to exogenous alkylating agents, particularly N-nitroso compounds, has been associated with increased incidence of primary human brain tumors, while intrinsic risk factors are currently unknown. The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) is a major defense against the carcinogenicity of N-nitroso compounds and other alkylators. We report here that in 55% (64/117) of cases, histologically normal brain tissue adjacent to primary human brain tumors lacked detectable MGMT activity [methyl excision repair-defective (Mer-) status]. The incidence of Mer- status in normal brain tissue from brain tumor patients was age-dependent, increasing from 21% in children 0.25-19 years of age to 75% in adults over 50. In contrast, Mer- status was found in 12% (5/43) of normal brain specimens from patients operated for conditions other than primary brain tumors and was not age-dependent. The 4.6-fold elevation in incidence of Mer- status in brain tumor patients is highly significant (chi2 = 24; p < or = 0.001). MGMT activity was independent of age in the lymphocytes of brain tumor patients and was present in lymphocytes from six of nine tumor patients whose normal brain specimen was Mer-. DNA polymerase beta, apurinic/apyrimidinic endonuclease, and lactate dehydrogenase activities were present in all specimens tested, including Mer- specimens from brain tumor patients. Our data are consistent with a model of carcinogenesis in human brain in which epigenetically regulated lack of MGMT is a predisposing factor and alkylation-related mutagenesis is a driving force.

Adolescent↗