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R Wallace

Publications and source records attributed to R Wallace.

At least 37 records · Page 2Linked to original sources
PubMed2001

How proxies make decisions about research for patients with Alzheimer's disease.

We examined the proxy decision-making and informed consent processes for clinical research involving 49 patient-subjects with dementia in an outpatient setting by performing serial in-depth, structured, open-ended telephone interviews. Interviews were tape recorded and transcribed. Transcripts were then coded and analyzed. Although in all cases proxy consent was obtained for research from a legally authorized representative, proxies reported considerable ambiguity regarding who made the decision to participate in research, or to what degree the decision was that of the proxy or of the patient. Reasons proxies gave for participating in research included: hope of direct or indirect benefits to the patient, caregiver, or patient's descendents; desperation; trust in the investigator; belief in the goodness of research; and altruism. These reasons varied according to the type of research. For instance, in drug trials hope of direct benefit prevailed; in studies not evaluating a potential therapy more altruistic concerns predominated. Being a proxy decision maker for research can be burdensome. The degree of burden related to making a decision to participate in research seems influenced by a number of intersecting factors, most importantly, the risk and nature of the study, the extent to which patients were able to participate in the decision, and the duration and severity of dementia. Proxy decision-making concerning participation in research for patients with dementia can be a difficult task. The process might be improved by emphasizing that proxy consent is being sought because the nature of the patient's underlying medical condition can preclude the ability to make meaningful decisions. In addition, clinical researchers should recognize that giving proxy consent might place additional burdens on caregivers and discuss this explicitly when proxy consent is solicited.

Aged↗
PubMed2001

Radiosurgery and stereotactic radiation therapy of skull base meningiomas: proposal of a grading system.

OBJECTIVE: The development of a grading system to guide treatment selection, and predict treatment difficulty and outcome of skull base meningiomas infiltrating the cavernous sinus which are managed by stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT), based on an 8-year experience with stereotactic radiation of skull base meningiomas. METHODS: T1 gadoliniun-enhanced magnetic resonance imaging (MRI) of 40 patients with skull base meningiomas, with or without prior surgery, who underwent radiosurgery or stereotactic radiation therapy from 1991 to 1998 at the UCLA Medical Center were reviewed, and the result of treatment was related to the tumor grade. Grade was based on tumor infiltration of the cavernous sinus and extension into adjacent structures. Treatment was performed with a linac-based system. The dose prescribed to the periphery of the tumor for SRS patients (n = 34) ranged from 12 to 22 Gy, and the maximum dose delivered to the tumor ranged from 24 to 46 Gy. SRT (n = 6). Treatment was planned using a single isocenter, usually prescribed to the 90% isodose volume, bringing the fractionation scheme to the maximal tolerance of the optic apparatus. The periphery dose ranged from 24 to 46 Gy with a maximum dose of 45 to 51 Gy. Clinical and MRI follow-up was performed every six months for the first 3 years and every year thereafter. RESULTS: Grade I meningiomas were restricted to the cavernous sinus (n = 12). Grade II cavernous sinus meningiomas extended to the clivus and/or the petrous bone, without compression of the brainstem (n = 9). Grade III meningiomas had superior and/or anterior extension with compression of the optic nerve or tract (n = 9). Grade IV tumors compressed the brain stem (n = 8), and Grade V were bilateral lesions (n = 2). Tumor control rates were 90% for Grade I, 86% for Grade II, 86% for Grade III, 42% for Grade IV and no control for tumors Grade V. Complications were not related to tumor grade. CONCLUSION: This grading system correlated with outcome and difficulty in planning radiosurgery. Failure of treatment was more likely to occur in patients with higher Grade tumors.

Adult↗
PubMed2001

A normative reference database study for Pronosco X-posure System.

Cortical width from radiographs has been used for more than 40 yr as a means of estimating bone strength. In the last 5-10 yr, increased availability of computers and the development of automated algorithms for image assessment have led to an increased interest in radiogrammetry. In this study, we examined a new radiogrammetry device, the Pronosco X-posure System, which estimates bone mineral density (BMD) from forearm/hand radiographs. We obtained hand and forearm radiographs and performed dual X-ray absorptiometry (DXA) at the wrist and hip on 832 women ages 20-79 at four clinical centers across the United States. We then used the X-posure System to estimate BMD (DXR-BMD). The goal of the study was to establish reference ranges for the method and to compare the measurement to DXA measurements of BMD at the wrist and hip. Using statistical models, we estimated that the peak value for DXR-BMD occurred at age 38 (mean = 0.598 g/cm2, standard deviation = 0.034 g/cm2). The correlation between DXR-BMD and DXA was 0.90 at the wrist and 0.61 at the hip. The relationship of DXR-BMD to reported history of fracture was of similar magnitude to that for DXA at the wrist and hip. The strong correlation of DXR-BMD from the X-posure System with DXA at the wrist from the Hologic machine suggests that the X-posure System may be an alternative to DXA at the wrist for the assessment of osteoporosis.

Absorptiometry, Photon↗
PubMed2001

Distortion of teatree stems by twine as a means to determine the number of years that the stems have been used to support cannabis plants.

In New Zealand, stems of teatree (Kunzea/Leptospermum) growing around illicit cannabis plots have been used to anchor lengths of twine running through the plots to hold cannabis plants upright. Forensic examinations of distortions of teatree stems caused by the twine have been carried out to determine when the twine had been first tied around the stems, in order to estimate the number of years that plots have been in operation. In this experiment, baling twine was tied around stems of a teatree (Kunzea ericoides) and the effect monitored for a period of three years. Varying degrees of stem distortion occurred during the first year, caused initially by expansion of callus (a wound tissue) rather than constriction of the growth (annual) rings of the xylem. Although this callus has a type of growth ring, these are not annual, therefore cannot be used to determine the number of years that stems have had twine attached. Xylem growth rings of the teatree in this experiment were not restricted until the third year. Distortion of teatree stems allows the determination of a minimum (not absolute) number of years that twine has been attached.

Journal Article↗
PubMed2000

Monitoring osteoporosis therapy with bone densitometry: misleading changes and regression to the mean. Fracture Intervention Trial Research Group.

CONTEXT: The principle of "regression to the mean" predicts that patients with unusual responses to treatment might represent outliers who are likely to have more typical responses if treatment is continued without change. OBJECTIVE: To test whether women who lose bone mineral density (BMD) during the first year of treatment for osteoporosis continue to lose BMD if the same treatment is continued beyond 1 year. DESIGN AND SETTING: Two randomized, double-blind, placebo-controlled trials in 11 US clinical research centers for the Fracture Intervention Trial and 180 centers in the United States and other countries for the Multiple Outcomes of Raloxifene Evaluation Trial. PARTICIPANTS AND INTERVENTIONS: Postmenopausal women with low BMD assigned to treatment with 5 mg/d of alendronate sodium in the Fracture intervention Trial who completed 2 years of BMD monitoring and adhered to study medication (n = 2634), and postmenopausal women with osteoporosis assigned to treatment with 60 or 120 mg/d of raloxifene hydrochloride in the Multiple Outcomes of Raloxifene Evaluation trial who similarly completed 2 years of monitoring while adhering to study medication (n = 3954). MAIN OUTCOME MEASURES: Baseline, 12-, and 24-month hip and spine BMD. RESULTS: Women with the greatest loss of BMD during the first year of treatment were the most likely to gain BMD during continued treatment. Specifically, among women taking alendronate whose hip BMD decreased by more than 4% during the first year, 83% (95% confidence interval [CI], 82%-84%)had increases in hip BMD during the second year, with an overall mean increase of 4.7%. In contrast, those who seemed to gain at least 8% during the first year lost an average of 1% (95% CI, 0.1%-1.9%) during the next year. Similar results were observed among women taking raloxifene for 2 years. CONCLUSIONS: Our data suggest that most women who lose BMD during the first year of treatment with alendronate or raloxifene will gain BMD if the same treatment is continued for a second year. These results illustrate the principle of regression to the mean and suggest that effective treatments for osteoporosis should not be changed because of loss of BMD during the first year of use.

Absorptiometry, Photon↗
PubMed2000

HLA and other host factors in transfusion-acquired HIV-1 infection.

The host and viral factors that underlie infection with HIV-1 vary considerably with some individuals progressing to AIDS within 3 to 5 years after infection, whereas others remain clinically asymptomatic for over 10 years. Host factors that may contribute to disease progression include HLA and allelic variants of the chemokine receptors CCR5 and CCR2, which have been shown to influence both long-term survival and rapid progression. In this study, we have examined the contribution of HLA and polymorphisms in CCR5 and CCR2 to long-term survival in transfusion-acquired HIV-1-infected individuals. We have found a higher number of HLA-A32 and -A25 alleles but a lower number of the HLA-B8 allele in the study group compared with the frequencies seen in the HIV-1-negative Australian caucasian population. However, there was no apparent contribution by allelic variants of CCR5 and CCR2 to long-term survival and the combined influence of HLA and CCR polymorphisms could not be evaluated in this relatively small (n = 20) group of study subjects. The results of this work support a role for HLA in long-term nonprogression though the presence in the Sydney Blood bank Cohort of nef-defective HIV-1 may confound associations between certain HLA alleles and long-term survival in the face of infection with HIV-1.

Adult↗
PubMed2000

Routine HLA-B genotyping with PCR-sequence-specific oligonucleotides (PCR-SSO) detects eight new alleles: B*0807, B*0809, B*1551, B*3529, B*3532, B*4025, B*5304 and B*5508.

This paper describes eight new alleles (B*0807, B*0809, B*1551, B*3529, B*3532, B*4025, B*5304 and B*5508) that have been found by routine HLA-B genotyping with sequence-specific oligonucleotides (SSOs). All of the new alleles have variations which cause changes in residues that occur within antigen binding pockets and T-cell recognition sites of the antigen. The new polymorphisms within these new alleles may affect the nature and specificity of peptide binding and cause differential T-cell activation, which may have an affect in transplantation.

Alleles↗
PubMed2000

The prognostic value of serum albumin in healthy older persons with low and high serum interleukin-6 (IL-6) levels.

OBJECTIVE: We sought to determine the prognostic value of serum albumin for 4-year mortality among high-functioning persons who did or did not have evidence of inflammation as indicated by high interleukin-6 (IL-6) levels. DESIGN: We used a case-cohort design of healthy, nondisabled older persons who had serum albumin and plasma IL-6 measured at baseline. Crude and multiply adjusted (for sociodemographics and chronic diseases) proportional hazards models were used to identify the effect of baseline levels of serum albumin level on 4-year mortality among those with higher and lower levels of IL-6. RESULTS: Among subjects without evidence of IL-6-mediated inflammation (IL-6 < 3.20 pg/mL), having a lower (< or = 4.4 g/dL) albumin level was associated with a multiply adjusted relative risk of 2.1 for 4-year mortality compared with those with higher albumin. In the presence of inflammation (IL-6 > or = 3.20 pg/mL), higher and lower serum albumin levels had similar risks (adjusted relative risks 4.0 and 3.8, respectively) compared with the referent group (higher albumin and low IL-6). CONCLUSIONS: High serum albumin has a protective effect in healthy older persons who do not have evidence of cytokine-mediated inflammation. This protective effect is not conferred in presence of inflammation. The mechanisms by which inflammation eliminates the protective effect of high albumin remain to be determined.

Aged↗
PubMed2000

Characteristics of nondisabled older persons who perform poorly in objective tests of lower extremity function.

OBJECTIVES: It has been suggested that nondisabled older persons with poor performance of lower extremity function are ideal targets for interventions of disability prevention. However, health-related factors associated with poor performance are largely unknown. Using data from a representative sample of nondisabled older persons, this study identifies the diseases and biological markers that characterize this group of the population. DESIGN AND PARTICIPANTS: A total of 3,381 persons aged 71 or older, interviewed and administered a battery of physical performance tests at the sixth annual follow-up of the Established Populations for Epidemiologic Studies of the Elderly (EPESE), who reported no need for help in walking 1/4 mile or climbing stairs. MEASUREMENTS: Lower extremity performance was measured using a short battery of tests including assessment of standing balance, a timed 2.4-m walk, and timed test of rising 5 times from a chair. Chronic conditions were ascertained as self-report of a physician diagnosis. Data on previous hospitalizations were obtained from the Medicare database. Nonfasting blood samples were obtained and processed with standard methods. RESULTS: In a multivariate analysis, older age, female gender, higher BMI, history of hip fracture and diabetes, one or more hospital admissions for acute infection in the last 3 years, lower levels of hemoglobin and albumin, and higher leukocytes and gamma-glutamyl transferase were all associated independently with poor performance. CONCLUSIONS: Screening for older patients who are not disabled but have poor lower extremity performance selects a subgroup of the population with a high percentage of women, high prevalence of diabetes and hip fracture, and high levels of biological markers of inflammation. This group represents about 10% of the US population 70 to 90 years old. These findings should be considered in planning specifically tailored interventions for disability prevention in this subgroup.

Activities of Daily Living↗
PubMed2000

Assessing the psychosocial impact of the ICD: a national survey of implantable cardioverter defibrillator health care providers.

The implantable cardioverter defibrillator (ICD) provides a survival advantage over antiarrhythmic medications for patients with life-threatening ventricular arrhythmias. However, the effect of ICD therapy on quality-of-life and psychosocial functioning are not as well understood. Health care providers (e.g., physicians, nurses) can serve as a valuable source of information related to these ICD outcomes. The purpose of this study was to investigate health care provider perceptions regarding: (1) the quality-of-life and psychosocial functioning of their ICD recipients, (2) the concerns or problems reported by ICD recipients, and (3) the degree of provider comfort in managing these concerns. The final sample of health care providers (n = 261) rated ICD recipients' global quality-of-life and psychosocial functioning, and specific concerns about health care, lifestyle, special population adjustment, marital and family adjustment, and emotional well-being. With regard to quality-of-life, health care providers reported that the majority of ICD recipients were functioning better (38%) or about the same (47%) than before implantation. However, health care providers reported that 15% of recipients experienced worse quality-of-life postimplantation. Similarly, health care providers indicated that 10%-20% of ICD recipients experienced worse emotional functioning and strained family relationships. Moreover, issues related to driving, dealing with ICD shocks, and depression were the most common ICD recipient concerns. Significant differences were noted between physicians and nurses/other health care professionals on a wide range of psychosocial issues. Health care providers generally reported the most comfort dealing with traditional medical issues (i.e., patient adherence), and the least comfort in managing emotional well-being issues (e.g., depression and anxiety). These results suggest that routine attention to ICD quality-of-life and psychosocial outcomes is indicated for health care providers who care for ICD recipients.

Adaptation, Psychological↗
PubMed1999

Neuromolecular computing: a new approach to human brain evolution.

Evolutionary approaches in human cognitive neurobiology traditionally emphasize macroscopic structures. It may soon be possible to supplement these studies with models of human information-processing of the molecular level. Thin-film, simulation, fluorescence microscopy, and high-resolution X-ray crystallographic studies provide evidence for transiently organized neural membrane molecular systems with possible computational properties. This review article examines evidence for hydrophobic-mismatch molecular interactions within phospholipid microdomains of a neural membrane bilayer. It is proposed that these interactions are a massively parallel algorithm which can rapidly compute near-optimal solutions to complex cognitive and physiological problems. Coupling of microdomain activity to permenant ion movements at ligand-gated and voltage-gated channels permits the conversion of molecular computations into neuron frequency codes. Evidence for microdomain transport of proteins to specific locations within the bilayer suggests that neuromolecular computation may be under some genetic control and thus modifiable by natural selection. A possible experimental approach for examining evolutionary changes in neuromolecular computation is briefly discussed.

Brain Chemistry↗
PubMed1999

Associations of elevated interleukin-6 and C-reactive protein levels with mortality in the elderly.

PURPOSE: To investigate whether interleukin-6 and C-reactive protein levels predict all-cause and cause-specific mortality in a population-based sample of nondisabled older people. SUBJECTS AND METHODS: A sample of 1,293 healthy, nondisabled participants in the Iowa 65+ Rural Health Study was followed prospectively for a mean of 4.6 years. Plasma interleukin-6 and C-reactive protein levels were measured in specimens obtained from 1987 to 1989. RESULTS: Higher interleukin-6 levels were associated with a twofold greater risk of death [relative risk (RR) for the highest quartile (> or = 3.19 pg/mL) compared with the lowest quartile of 1.9 [95% confidence interval, CI, 1.2 to 3.1]). Higher C-reactive protein levels (> or = 2.78 mg/L) were also associated with increased risk (RR = 1.6; CI, 1.0 to 2.6). Subjects with elevation of both interleukin-6 and C-reactive protein levels were 2.6 times more likely (CI, 1.6 to 4.3) to die during follow-up than those with low levels of both measurements. Similar results were found for cardiovascular and noncardiovascular causes of death, as well as when subjects were stratified by sex, smoking status, and prior cardiovascular disease, and for both early (<2.3 years) and later follow-up. Results were independent of age, sex, body mass index, and history of smoking, diabetes, and cardiovascular disease, as well as known indicators of inflammation including fibrinogen and albumin levels and white blood cell count. CONCLUSIONS: Higher circulating levels of interleukin-6 and C-reactive protein were associated with mortality in this population-based sample of healthy older persons. These measures may be useful for identification of high-risk subgroups for anti-inflammatory interventions.

Aged↗
PubMed1999

Role of motor unit number estimate electromyography in experimental canine laryngeal reinnervation.

Laryngeal electromyography has been used clinically to differentiate neuromuscular pathology from other causes of vocal fold immobility such as arytenoid dislocation, tumor invasion, or cricoarytenoid joint fixation. Electromyography has also been used to predict the prognosis for nerve recovery in laryngeal paralysis. Existing electromyographic techniques either record activity with voluntary motion or study nerve conduction. In this study a new technique, motor unit number estimation, a commercially available quantitative method of electromyographic analysis, is used to study the progress of recovery of vocal fold function after recurrent laryngeal nerve injury. Four dogs underwent transection and immediate reanastomosis of selected branches of the adductor and abductor branches of the recurrent laryngeal nerve on 1 side; the opposite side served as a control. Baseline electromyographic and videolaryngoscopic studies were performed. These measures were then repeated in a longitudinal fashion every 6 weeks after denervation. The motor unit number estimation technique indicated a return of motor unit numbers with time, along with estimates of their size. This was consistent with the expected progress of laryngeal reinnervation. These data and their predictive value for nerve recovery will be discussed.

Anastomosis, Surgical↗
PubMed1999

Organisms, organizations and interactions: an information theory approach to biocultural evolution.

The language metaphor of theoretical biology, proposed by Waddington in 1972, provides a basis for the formal examination of how different self-reproducing structures interact in an extended evolutionary context. Such interactions have become central objects of study in fields ranging from human evolution-genes and culture-to economics-firms, markets and technology. Here we use the Shannon-McMillan Theorem, one of the fundamental asymptotic relations of probability theory, to study the 'weakest' and hence most universal, forms of interaction between generalized languages. We propose that the co-evolving gene-culture structure that permits human ultra-sociality emerged in a singular coagulation of genetic and cultural 'languages', in the general sense of the word. Human populations have since hosted series of culture-only speciations and coagulations, events that, in this formulation, do not become mired in the 'meme' concept.

Biological Evolution↗
PubMed1999

Occupational tuberculosis among deputy sheriffs in Connecticut: a risk model of transmission.

OBJECTIVES: The purpose of this study was to identify risk factors for tuberculin skin test conversions among non-infected deputy sheriffs in Connecticut and during an out-break in an urban lock-up. METHODS: 377 tuberculin skin-test negative sheriffs statewide in 1994-1995 and 37 sheriffs in the lock-up in 1995 were screened and questionnaires administered. Cellblock volumetric air flow was measured. The Wells-Riley model of airborne transmission [C = S(1-e-Iqpt/Q)] was applied to the epidemiologic and ventilation data. RESULTS: Statewide, of 377 sheriffs screened, 22 (5.8%) had positive skin tests. Risk factors included older age (p < .0075) and longer tenure (p < .036). In the lock-up, of 37 sheriffs screened, 4 (10.8%) had positive skin tests. Measured mean outside air flow per occupant (8.0 cfm; S.D. = 2.2) was below design (15 cfm) and recommended (20 cfm) standards. Mathematical modeling estimated that TB transmission would be reduced by 62.5 percent with ventilation at design specifications. CONCLUSIONS: Inadequate ventilation may increase the risk for occupational transmission of tuberculosis. Since lock-ups do not have the time to conduct inmate TB screenings, supplemental engineering controls may be required.

Adult↗