Biomedical subjects
R White
Publications and source records attributed to R White.
Multicenter phase II study to evaluate a 28-day regimen of oral fluorouracil plus eniluracil in the treatment of patients with previously untreated metastatic colorectal cancer.
PURPOSE: To determine the efficacy of fluorouracil (5-FU) plus eniluracil when administered to patients with previously untreated metastatic colorectal cancer. PATIENTS AND METHODS: In this single-arm phase II study, patients with previously untreated metastatic colorectal cancer received oral eniluracil plus 5-FU (10:1 dose ratio), at 5-FU doses of 1.00 mg/m(2) or 1.15 mg/m(2) twice daily (every 12 hours) for 28 consecutive days repeated every 5 weeks (one cycle). Treatment continued until there was documented disease progression or unacceptable toxicity. RESULTS: Thirty and 25 patients were enrolled at a starting dose of 1.00 mg/m(2) and 1.15 mg/m(2), respectively. Fourteen (25%) of 55 patients (95% confidence interval, 15% to 39%) had a partial response, and 20 patients (36%) had stable disease. The median durations of the partial responses and stable disease were 23.9 weeks (range, 12.3 to 52.1+ weeks) and 24.1 weeks (range, 17.1 to 55.6+ weeks), respectively. The median durations of progression-free and overall survival were 22.6 weeks (range, 21.0 to 29.0 weeks) and 59 weeks (range, 4 to 84+ weeks), respectively. The response rate in the 1.15 mg/m(2)-dose group was similar to the 1.00 mg/m(2)-dose group (28% v 23%, respectively). Severe (grade 3/4) nonhematologic treatment-related toxicity included diarrhea (nine patients), nausea/vomiting (one patient each), mucositis (two patients), and anorexia (one patient). Severe hematologic toxicities were rare. At the 1.15 mg/m(2)-dose level, two patients exhibited grade 3 granulocytopenia, and two patients had grade 3 anemia. CONCLUSION: The response rate with oral 5-FU plus eniluracil is comparable with that observed with infusional 5-FU or bolus 5-FU and leucovorin. The toxicity profile of this oral regimen is acceptable for use in an outpatient home-based setting.
An insurer's perspective on reform.
Individual health insurance markets differ from state to state, and as a result approaches to individual market reforms need to be different. In evaluating approaches, policy makers need to remember that since the decision to purchase health insurance coverage is voluntary, the potential for adverse selection exists. In addition, rather than putting the focus of individual market reforms almost exclusively on access to health insurance for a small number of persons with high-cost health conditions, more attention needs to be put on how to decrease the number of uninsured persons. This includes making the premiums paid for individual health insurance 100 percent tax deductible, similar to those of employer-based health insurance. Finally, market reforms need to treat all types of coverage issued in the individual market the same, whether they are purchased direct for the insurer or through an out-of-state association.
The influence of hypoxia on the relative sensitivity of human tumor cells to 62.5 MeV (p-->Be) fast neutrons and 4 MeV photons.
Fast neutrons have been used in the clinical radiation therapy of tumors largely because of experimental evidence that their cytotoxic effects are much less dependent on oxygen levels than those of low-LET photons. The potential therapeutic advantage of fast neutrons based on hypoxia alone can be calculated as the "hypoxic gain factor", which is the ratio of the OERs for the fast-neutron compared to the photon beams. The hypoxic gain factor that is generally anticipated based on studies with established mammalian cell lines is about 1.6. However, surprisingly few studies have examined the influence of hypoxia on the fast-neutron radiosensitivity of human tumor cells of different histological types. For this reason, we have determined the OERs of five human tumor cell lines exposed to 62.5 MeV (p-->Be) cyclotron-generated fast neutrons or 4 MeV photons from a clinical linear accelerator. The OERs for four chemotherapy-naive cell lines, HT29/5, Hep2, HeLa and RT112, were invariably greater for photons than for neutrons, but all of these values were lower than expected on the basis of the previous literature. Despite their low OERs, these cell lines showed hypoxic gain factors that were within the range of 1.31-1.63, indicating that such effects cannot entirely explain the disappointing clinical results obtained with fast neutrons. In contrast, comparison of the surviving fractions at clinically relevant doses (1.6 Gy of neutrons and 2.0 Gy of photons) for these four tumor cell lines suggested that little benefit should result from neutron treatment. Only the cisplatin-resistant OAW42-CP line showed a significant hypoxic gain factor by this method of analysis. We conclude that, at the dose fractions used in clinical radiation therapy, there may not be a radiobiological precedent for higher local control rates after fast-neutron irradiation of hypoxic tumor cells.
Weighing MSDS management programs.
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Technology and the evolution of human genetics.
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Toxicity evaluation of petroleum blending streams: reproductive and developmental effects of light catalytic cracked naphtha distillate in rats.
A distillate of light catalytic cracked naphtha (CAS number 64741-55-5, LCCN-D), administered by inhalation, was tested for reproductive and developmental toxicity in Sprague-Dawley rats, following a modified OECD Guideline 421, Reproductive/Developmental Toxicity Screening Protocol. LCCN-D was administered as a vapor, 6 h/d, 7 d/wk at target concentrations of 0, 750, 2500 or 7500 ppm to female rats for approximately 7 wk from 2 wk prior to mating, during mating through gestational d 19, and to males beginning 2 wk prior to mating for 8 consecutive weeks. Dams and litters were sacrificed on postnatal d 4, and males were sacrificed within the following week. Parental systemic effects observed at the 7500 ppm exposure level were increased kidney weights and relative liver weights in males and increased spleen weights in high-dose females. Livers and spleens from rats in the high-dose group were normal in appearance at necropsy. IncreaSed kidney weights in high-dose males were indicative of male-rat-specific light hydrocarbon nephropathy. No test-related microscopic changes were observed in the reproductive organs or nasal turbinate tissues of either sex. Reproductive performance was unaffected by treatment with LCCN-D. Fertility index was > or =90% in all dose groups. There were no exposure-related differences in implantation sites and live pups per litter, and no gross abnormalities were observed. Pups born from treated dams showed comparable body weights and weight gains to controls. The viability index on postpartum d 4 was > or =97%; the high-dose group had more male than female pups at birth and at d 4 postpartum. Under the conditions of this study, the no-observable-adverse-effect level (NOAEL) for exposure to light catalytic cracked naphtha distillate for parental toxicity was 2500 ppm and the NOAEL for reproductive performance and developmental toxicity was 7500 ppm.
Temporal trends in the use of anticoagulants among older adults with atrial fibrillation.
BACKGROUND: Several recent randomized clinical trials have demonstrated that warfarin sodium treatment, and to a lesser extent aspirin, reduces risk of stroke and death compared with placebo in persons with atrial fibrillation. Insufficient documentation exists on the extent to which the use of these therapies following trial publications has continued to increase in the elderly with atrial fibrillation. METHODS: We used data from the Cardiovascular Health Study, a study of 5888 community-dwelling adults aged 65 years or older, to determine the prevalence of warfarin and aspirin use in persons with electrocardiogram-identified atrial fibrillation. Electrocardiogram examinations were conducted at baseline from 1989 through 1990, and at 6 subsequent annual examinations through 1995-1996. Medication data were collected by inventory methods at each examination. Temporal change in use of anticoagulants was analyzed by comparing percentage use in 1990 to use in each year through 1996. RESULTS: The use of warfarin increased 4-fold from 13% in 1990 to 50% in 1996 among participants with prevalent atrial fibrillation (P<.001). Daily use of aspirin did not increase over time. Participants younger than 80 years were 4 times more likely to use warfarin in 1996 (P<.001) than those 80 years and older. Use of aspirin did not vary significantly with age. CONCLUSIONS: Warfarin use in community-dwelling elderly persons with electrocardiogram-documented atrial fibrillation increased steadily following the first publication of its treatment benefit, reaching 50% by 1996. In contrast, use of aspirin was unchanged during this same period. Continued efforts to promote appropriate anticoagulation therapy to physicians and their patients may still be needed.
Apc1638T: a mouse model delineating critical domains of the adenomatous polyposis coli protein involved in tumorigenesis and development.
The adenomatous polyposis coli (APC) gene is considered as the true gatekeeper of colonic epithelial proliferation: It is mutated in the majority of colorectal tumors, and mutations occur at early stages of tumor development in mouse and man. These mutant proteins lack most of the seven 20-amino-acid repeats and all SAMP motifs that have been associated with down-regulation of intracellular beta-catenin levels. In addition, they lack the carboxy-terminal domains that bind to DLG, EB1, and microtubulin. APC also appears to be essential in development because homozygosity for mouse Apc mutations invariably results in early embryonic lethality. Here, we describe the generation of a mouse model carrying a targeted mutation at codon 1638 of the mouse Apc gene, Apc1638T, resulting in a truncated Apc protein encompassing three of the seven 20 amino acid repeats and one SAMP motif, but missing all of the carboxy-terminal domains thought to be associated with tumorigenesis. Surprisingly, homozygosity for the Apc1638T mutation is compatible with postnatal life. However, homozygous mutant animals are characterized by growth retardation, a reduced postnatal viability on the B6 genetic background, the absence of preputial glands, and the formation of nipple-associated cysts. Most importantly, Apc1638T/1638T animals that survive to adulthood are tumor free. Although the full complement of Apc1638T is sufficient for proper beta-catenin signaling, dosage reductions of the truncated protein result in increasingly severe defects in beta-catenin regulation. The SAMP motif retained in Apc1638T also appears to be important for this function as shown by analysis of the Apc1572T protein in which its targeted deletion results in a further reduction in the ability of properly controlling beta-catenin/Tcf signaling. These results indicate that the association with DLG, EB1, and microtubulin is less critical for the maintenance of homeostasis by APC than has been suggested previously, and that proper beta-catenin regulation by APC appears to be required for normal embryonic development and tumor suppression.
Regulation of beta-catenin signaling by the B56 subunit of protein phosphatase 2A.
Dysregulation of Wnt-beta-catenin signaling disrupts axis formation in vertebrate embryos and underlies multiple human malignancies. The adenomatous polyposis coli (APC) protein, axin, and glycogen synthase kinase 3beta form a Wnt-regulated signaling complex that mediates the phosphorylation-dependent degradation of beta-catenin. A protein phosphatase 2A (PP2A) regulatory subunit, B56, interacted with APC in the yeast two-hybrid system. Expression of B56 reduced the abundance of beta-catenin and inhibited transcription of beta-catenin target genes in mammalian cells and Xenopus embryo explants. The B56-dependent decrease in beta-catenin was blocked by oncogenic mutations in beta-catenin or APC, and by proteasome inhibitors. B56 may direct PP2A to dephosphorylate specific components of the APC-dependent signaling complex and thereby inhibit Wnt signaling.
Trandolapril and human diabetic neuropathy.
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Natural killer cells in relapsing-remitting MS: effect of treatment with interferon beta-1B.
OBJECTIVE: To determine the effect of treatment with interferon beta-1b (IFN-beta) on natural killer (NK) cell function and phenotype in relapsing-remitting MS (RRMS) patients, and their relationship to disease activity assessed both clinically and with serial MRI. BACKGROUND: NK cells may play a role in the immunopathogenesis of MS. Previously the authors reported a positive relationship between mean NK cell functional activity (FA) and total number of active lesions on MRI in a serial study of RRMS. Cycles in NK cell FA over time created a series of peaks and valleys, and a significant relationship has been identified between the valleys and the appearance of active lesions on MRI or onset of clinical attacks. The development of valleys in NK cell FA before the appearance of active lesions on MRI was statistically significant. METHODS: The authors studied the effect of alternate-day therapy with 8.0 mIU (high dose [HD]) or 1.6 mIU (low dose [LD]) IFN-beta on NK cell FA, assessed by an in vitro 51Cr release K-562 target cell assay, and phenotype determination in RRMS patients. RESULTS: Treatment with HD IFN-beta results in an inverse relationship between mean NK cell FA and total number of active lesions on MRI over 2 years. A stronger inverse relationship was found in those patients who did not develop neutralizing antibodies to IFN (HD-) compared with a positive relationship in those who did (HD +). Treatment with IFN-beta did not affect the cyclic nature of NK cell FA, mean NK cell FA, variability around the mean, mean length of the cycle, time spent in valleys and peaks, or the significant relationship between the appearance of active lesions on MRI/onset of clinical attacks and valleys in NK cell FA. In contrast, treatment with HD but not LD IFN-beta did result in a significant reduction in CD57+ (a cell surface marker for subsets of NK cells) peripheral blood lymphocytes (PBL) compared with placebo. This effect, which originated largely from the HD- group of patients, developed shortly after treatment was initiated and was maintained throughout the study. CONCLUSIONS: RRMS patients with higher mean NK cell FA may be not only at greater risk for the development of active lesions but also may be more likely to respond to IFN-beta. Development of neutralizing antibodies to IFN-beta could interfere with this effect. This effect may be mediated through an action on a CD57+ subset of PBL.
Endovascular vs open abdominal aortic aneurysm repair: a comparison of cardiac morbidity and mortality.
HYPOTHESIS: Adverse cardiac event rates following endovascular abdominal aortic aneurysm (EAAA) and open abdominal aortic aneurysm (OAAA) repair are similar. We also hypothesized that the Eagle criteria (Q wave on electrocardiogram, diabetes, angina, congestive heart failure, age >70 years, and ventricular ectopy) are useful predictors of cardiac events in patients undergoing EAAA repair. DESIGN: Prospective (patients undergoing EAAA repair) and retrospective (patients undergoing OAAA repair). SETTING: Public teaching and Veterans Affairs medical centers. PATIENTS: Eighty-three EAAA and 63 OAAA repairs. MAIN OUTCOME MEASURES: Myocardial infarction, congestive heart failure, and cardiac death. RESULTS: Patients with EAAA were older (73 vs 68 years, P=.003). There were no differences in the mean number of Eagle criteria (1.2 vs 1.3), cardiac event rates (6% vs 4.8%), or mortalities (3.6% vs 4.8%). Within the EAAA group, congestive heart failure (P=.005) and Q wave on electrocardiogram (P=.006) were the only predictors of cardiac events. CONCLUSIONS: Patients undergoing OAAA and EAAA repair had similar cardiac event rates and mortality. In patients undergoing EAAA repair, history of congestive heart failure and Q wave on electrocardiogram were predictors of cardiac events.
The identical 5' splice-site acceptor mutation in five attenuated APC families from Newfoundland demonstrates a founder effect.
Inherited mutations of the APC gene predispose carriers to multiple adenomatous polyps of the colon and rectum and to colorectal cancer. Mutations located at the extreme 5' end of the APC gene, however, are associated with a less severe disease known as attenuated adenomatous polyposis coli (AAPC). Many individuals with AAPC develop relatively few colorectal polyps but are still at high risk for colorectal cancer. We report here the identification of a 5' APC germline mutation in five separately ascertained AAPC families from Newfoundland, Canada. This disease-causing mutation is a single basepair change (G to A) in the splice-acceptor region of APC intron 3 that creates a mutant RNA without exon 4 of APC. The observation of the same APC mutation in five families from the same geographic area demonstrates a founder effect. Furthermore, the identification of this germline mutation strengthens the correlation between the 5' location of an APC disease-causing mutation and the attenuated polyposis phenotype.
Cardiac morbidity and operative mortality following lower-extremity amputation: the significance of multiple Eagle criteria.
The ability of the Eagle criteria (age >70 years, angina, diabetes, Q wave on EKG, history of congestive heart failure) to predict adverse cardiac events following major vascular surgery has previously been demonstrated. However, the utility of these criteria for lower-extremity amputation is not well established. To determine the value of the Eagle criteria for predicting cardiac morbidity and operative mortality following major lower-extremity amputation, we reviewed 214 consecutive procedures performed at two institutions over a 3-year period. Mean age was 62.7 years and 85% of the patients were male. Diabetes was the most frequent Eagle criterion (74%). The mean number of Eagle criteria was 1.6. Fifty-six percent of the amputations were below the knee, 24% were above the knee, and 20% were guillotine. On multivariate regression analysis, the presence of two or more Eagle criteria (16% vs. 4%, p = 0.04) and decompensated heart failure (39% vs. 7%, p = 0.003) were predictive of adverse cardiac events. The only predictor of postoperative mortality was the presence of two or more Eagle criteria (15% vs. 4%, p = 0.004). Our evaluation of the results of this study led us to conclude that patients requiring major lower-extremity amputation for major vascular disease who have multiple Eagle criteria or decompensated congestive heart failure are at high risk for adverse cardiac events and postoperative death. These findings should be used to guide perioperative cardiac evaluation and therapy.
The variability of force platform data in normal and cerebral palsy gait.
OBJECTIVE: To determine the natural variability and symmetry of force platform parameters in normal and cerebral palsy gait. DESIGN: Force platform data has been analysed using coefficient of variation, analysis of variances and symmetry index. BACKGROUND: It is important to establish the natural variability of force platform data so that changes in gait due to natural variability and those due to intervention can be determined. METHODS: Force platform data and walking speed were recorded in 15 normal volunteers and 11 children with cerebral palsy on 3 consecutive days. Five recordings were made of each leg on each day. RESULTS: The force platform parameters in both groups showed greater asymmetry in the horizontal plane. In the cerebral palsy group significant asymmetry was found in all 3 directions. The variation of the vertical ground reaction force peaks (Fz1 and Fz3) and of the anterior-posterior negative peak (Fy3) for both groups was low. Fz3 was the most reproducible force parameter. The other force parameters showed high variability and are not considered reliable measures of gait. The temporal parameters and the walking speed were reproducible measures. CONCLUSIONS: Only selected ground reaction force parameters showed acceptable stability and reproducibility. Therefore caution has to be taken in the selection of these parameters, when assessing the effects of any intervention on cerebral palsy gait.
HIV-risk behaviors in adolescent substance abusers.
Thirty adolescents aged 12-18 years from each group (substance use disorders, psychiatric disorders, and controls) were assessed to explore HIV-risk behaviors and knowledge about HIV/AIDS. Semi-structured instruments for psychiatric and substance use disorders were also administered. There were no significant differences between groups in knowledge of HIV/AIDS. However, chi-square analysis of risk behaviors revealed significant differences between the substance use disorders group and the controls. The knowledge-behavior gap was greater for the substance users than all other groups, in that while they knew an equal amount about HIV/AIDS, they actually engaged in more risky sexual behaviors than the other two groups. It may be that the impulsivity associated with substance use disorders accounts for this difference. It is recommended that HIV/AIDS prevention education and impulse control strategies are included in the treatment of adolescents with substance use disorders.
Assessment of patients for orthognathic surgery.
Rapid advances in orthognathic surgery now allow the clinician to treat severe dentofacial deformities that were once only manageable by orthodontic camouflage. These cases were often compromised with unacceptable facial esthetics and unstable occlusal results. Over the past 25 years, there have been numerous improvements in technology and the surgical management of dentofacial deformities. These progressions now allow more predictable surgical outcomes, which ensure patient satisfaction. Not all patients are candidates for surgical treatment; therefore, patient assessment and selection remains paramount in the process of diagnosing and treatment planning for this type of irreversible treatment. The inclusion of patients in the decision-making process increases their awareness and acceptance of the final result. The past three decades indicate an increased usage of orthodontic treatment by both children and adults. Patient demographic profiles for severe occlusal and facial characteristics are presented in an effort to understand the epidemiological factors of malocclusion and predict the population's need for this service.