PubMed Health⌕ Search

Biomedical subjects

R C Petersen

Publications and source records attributed to R C Petersen.

At least 19 recordsLinked to original sources
PubMed1992

Prescription drug diversion control and medical practice.

Concern about the role of prescription drug diversion in drug abuse has led to demands for more stringent regulation and for better ways to detect prescription drug diversion. Advances in technology now allow point-of-sale computer systems to report prescriptions filled by pharmacies to state agencies rapidly and possibly more economically. However, the advantages of more comprehensive control systems must be balanced against their possible effects on medical practice and patient care. Our limited knowledge about prescription drug diversion and the impact of diversion control systems on medical practice is summarized. Needed research is outlined together with the components of a diversion control program that balances reducing drug diversion with minimizing adverse effects on medical practice and patient care. We stress the need for broadly defined practice parameters and peer review by medical experts thoroughly familiar with the complexities of medical practice.

Clinical Pharmacy Information Systems↗
PubMed1992

Radio-frequency electromagnetic fields associated with cellular-radio cell-site antennas.

Because of a heightened public awareness of issues pertaining to the use of electromagnetic energy, concurrent with a rapid growth of the cellular telephone industry, a study was initiated to characterize the electromagnetic environment associated with typical cell-site antennas. In particular, the radio-frequency electromagnetic (RF) fields in the vicinity of several antenna towers, ranging in height from 46-82 m, were characterized by measurement. In all cases, the antennas were omnidirectional co-linear arrays. The maximal power densities considered representative of public exposure were found to be less than 100 microW/m2 (10 nW/cm2) per radio channel. Comparison of measured values with the corresponding values that were calculated from the free-space transmission formula indicated that the analytical technique is conservative (i.e., overestimates field levels). The measured and corresponding analytical values were found to be well below accepted exposure limits even when extrapolated to simultaneous and continuous operation of the maximal number of transmitters that would be expected to be installed at a cell-site. Additional measurements were made in the near field of the same antenna type in a roof-mounted configuration. At a distance of 0.7 m from the antenna, the maximal power density in the main beam was found to be less than 30 W/m2 (3 mW/cm2) when normalized to sixteen radio channels (the maximal number used on a single antenna) and less than 30 mW/m2 (3 microW/m2) at 70 m. In all cases, the effective radiated power (ERP) by each radio channel was 100 W referenced to a half-wave dipole. This paper describes the instrumentation and measurement techniques used for this study and provides a summary of the results.

Electromagnetic Phenomena↗
PubMed1992

Acute confusional state. Don't mistake it for dementia.

Acute confusional state is a condition that is commonly encountered in many types of medical practice. Certain patients, especially the elderly, are vulnerable to the disorder, and recognition of this fact can help prevent the development or minimize the severity of the condition. Thorough history taking and evaluation often point to the underlying cause, and attention to general principles of environmental and pharmacologic management can minimize morbidity.

Acute Disease↗
PubMed1992

MR-based hippocampal volumetry in the diagnosis of Alzheimer's disease.

We evaluated a new magnetic resonance (MR)-based technique for performing volumetric measurements of temporal lobe structures. The technique was designed to assist in making the clinical diagnosis of dementia of the Alzheimer type (DAT). We chose specific anatomic regions of interest because of their known involvement in memory function and in the neuropathology of DAT and used a regression model to assess the effects of age on the volumes of the anterior temporal lobe (ATL) and the hippocampal formation (HF). These measurements were normalized by total intracranial volume (TIV). The volumetric measurements of both the normalized ATL and HF were significantly smaller (p less than 0.001) in DAT patients (N = 20) than in controls (N = 22), but the HF volumes provided much better separation between the two groups. Eighty-five percent of the DAT patients fell below the range of the HF/TIV measurement for the control subjects. This separation held up over the entire age range studied. Normalized volumes of both the HF and ATL decreased with age significantly for both the DAT patients and the controls. These results support the contention that MR-based HF volumetric measurements are accurate in differentiating DAT patients from cognitively normal elderly individuals. This technique may be a useful adjunct in making the clinical diagnosis of DAT.

Aged↗
PubMed1992

Memory function in normal aging.

We evaluated memory function in a group of 161 community-dwelling, cognitively normal individuals aged 62 to 100 years recruited as part of the Mayo Clinic Alzheimer's Disease Patient Registry. We used the Free and Cued Selective Reminding Test and the Rey Auditory Verbal Learning Test to evaluate two aspects of memory function thought to be sensitive to the effects of aging: learning (acquisition) and delayed recall (forgetting). The results were quite consistent and demonstrated that learning or acquisition performance declines uniformly with increasing age but is not related to education. Delayed recall or forgetting, however, remained relatively stable across age when adjusted for the amount of material initially learned. These findings are relevant for assessing normal memory function relative to the early impairments found in dementia and form a baseline against which memory performance can be assessed by the clinician. In particular, suspicion regarding a disorder of brain function affecting memory processes should be raised if learning performance declines more rapidly than expected or if delayed recall is impaired to any significant extent.

Aged↗
PubMed1992

Asymmetric cortical degenerative syndromes: clinical and radiologic correlations.

Eight patients presented with slowly progressive focal neurologic syndromes that conformed to one of three clinically defined categories: progressive nonfluent aphasia (three patients), progressive perceptual-motor impairment (four patients), and progressive frontal lobe syndrome (one patient). Planar MRI and MRI-based surface or volume renderings demonstrated focal areas of atrophy that correlated well with clinical deficits. Single-photon emission computed tomography (SPECT) showed areas of cortical hypoperfusion that corresponded to focally atrophic regions revealed by MRI, but abnormal areas with SPECT were larger than those suggested by MRI. MRI and SPECT are useful in defining the regional structural and functional cerebral abnormalities that underlie slowly progressive focal neurologic syndromes caused by asymmetric cortical degeneration.

Aged↗
PubMed1991

The short test of mental status. Correlations with standardized psychometric testing.

The Short Test of Mental Status can be administered to patients in inpatient and outpatient settings in approximately 5 minutes, and it contains items that test orientation, attention, immediate recall, arithmetic, abstraction, construction, information, and delayed (approximately 3 minutes) recall. The test was administered to a group of demented community patients and their age- and sex-matched control subjects. Using an age-adjusted approach, sensitivity of the test to identifying dementia is 86.4, with a specificity of 93.5. The test was compared with standardized tests of cognitive function such as the Wechsler Adult Intelligence Scale, Mattis Dementia Scale, and the Auditory Verbal Learning Test, and showed a high degree of correlation. Group means and standard deviations for subtest items and total score are presented for control subjects (n = 138), demented patients (n = 130), and patients with memory impairment only (n = 20). Percentile scores for subtest items in control subjects are also provided.

Aged↗
PubMed1991

Age-associated memory impairment diagnoses: problems of reliability and concerns for terminology.

Objective memory criteria for diagnosing age-associated memory impairment (AAMI), age-consistent memory impairment, and late-life forgetfulness (LLF) were applied to 523 cognitively normal older persons divided into 2 groups on the basis of the clinical memory assessment battery they received. Seventy-seven percent of Group 2 and 98% of Group 1 met the Crook et al. (1986) cognitive criteria for AAMI on at least 1 test. Rates based on individual tests varied from 7% to 96%. Objective-cognitive criteria for LLF were met by no members of Group 1 but by 31% of Group 2. Results suggest that, as proposed, the criteria for age-related diagnoses lack reliability. Concerns regarding the diagnosis of normal memory in older populations are considered.

Aged↗
PubMed1991

Radiofrequency/microwave protection guides.

Limits for exposure to electromagnetic fields at RF and microwave frequencies have, at times, been subject to criticism and controversy. In many cases the controversy results from a lack of absolute proof that some nominal levels of exposure are safe, from a misunderstanding of how to apply the limits, and from a lack of understanding (by critics) of the rationale upon which the limits were developed and of the consensus process required for approval. Exposure limits, based on rather simple models, were developed during the early 1950s and have been used extensively without revision for almost three decades (and still are by various organizations including the U.S. Department of Labor). During the past decade, however, these limits have been modified extensively to reflect both the increase in knowledge of bioeffects associated with exposure to electromagnetic energy and the advances in dosimetry and, also, to overcome obvious shortcomings in the earlier exposure guides. This paper will review the exposure criteria developed during the past decade by the American National Standards Institute and the National Council on Radiation Protection and Measurements, with particular emphasis on the underlying rationale.

Environmental Exposure↗
PubMed1989

Bioavailability of aluminium in the presence of humic substances at low and moderate pH.

Fish kills have been observed in lakes with low pH and high Al content. The monomeric inorganic Al seems to be the most acute toxic fraction. Humic lake waters, situated in acidified areas, often have high values of aluminium. However, the fraction of Al bound to humus is regarded as a relatively nontoxic form of Al. As pH is decreasing, the physical and chemical properties of humus change. The molecular size, electronegativity and colour decrease. An important question in this matter is the potential change in bioavailability of "Al-humus" as pH decreases. The bioavailability of the Al-humus complex was studied; in relation to surface water acidification and in relation to drinking water and human health. The work is based on the octanol/water partition coefficient (Khow), estimated by measuring the UV absorption at 254 nm. Al concentration is determined in the water phase and in the octanol phase. The results show that the amount of organic material soluble in the octanol phase relative to the amount in the aqueous phase increases with decreasing pH, while no Al is detected in the octanol phase. It is concluded that Al is only weakly bound to humus and consequently Al complexed with humus is of minor concern in bioaccumulation.

Aluminum↗
PubMed1989

Cognitive and psychiatric abnormalities in multiple sclerosis.

In multiple sclerosis, behavioral changes, including alterations in cognitive functions and psychiatric abnormalities, have been recognized with increasing frequency in recent years. Multiple sclerosis formerly was thought to be primarily a disorder of the brain stem and spinal cord; however, functional changes that can be attributed, at least in part, to cerebral dysfunction are being recognized. Certain cognitive functions such as memory and conceptual processes seem to be preferentially impaired. The degrees of impairment of other functions such as attention and visuospatial skills are now being evaluated. Psychiatrically, affective disorders seem to be the most common diagnoses, and debate exists about whether these abnormalities are a function of the demyelinating process itself or are a reaction to the disability produced by the disorder.

Dementia↗
PubMed1989

Anterior temporal lobes and hippocampal formations: normative volumetric measurements from MR images in young adults.

Volumes of the right and left anterior temporal lobes and hippocampal formations were measured from magnetic resonance images in 52 healthy volunteers, aged 20-40 years. Subjects were selected by age, sex, and handedness to evaluate possible effect of these variables. Data were normalized for variation in total intracranial volume between individuals. Right-left asymmetry in the volumes of the anterior temporal lobes and hippocampal formations was a normal finding. The anterior temporal lobe of the non-dominant (right) hemisphere was larger than the left by a small (mean right-left difference, 2.3 cm3) but statistically significant amount (P less than .005) in right-handed subjects. No significant effect of age or sex was seen in normalized right or left anterior temporal lobe volume. The right hippocampal formation was larger than the left for all subjects by a small (mean right-left difference, 0.3 cm3) but statistically significant amount (P less than .001). No effect of age, sex, or handedness was seen in normalized hippocampal formation volumes.

Adult↗
PubMed1979

Scopolamine state-dependent memory processes in man.

Scopolamine state-dependent learning was investigated in man using four learning and recall tasks. Twenty-eight subjects performed the four tasks on the first day of the 2 day experiment under either the influence of the drug (5 microgram/kg of scopolamine administered IV) or a placebo and tried to recall the material on the second day in either the same or altered drug state. State-dependent learning theory predicts that those subjects in the same drug state on both days should recall more material than those who had their drug condition changed. Results confirmed this prediction for the two recall tasks which did not involve recall cues or prompts but not for the tasks involving memory acids. This implies that the drug state has memory cueing properties of its own and that recall can be enhanced either by restoring the drug state which existed at the time of learning or by providing external prompts.external prompts.

Adolescent↗
PubMed1979

Electromagnetic radiation emitted from video computer terminals.

There has been a developing concern about potential health hazards attributable to electromagnetic radiation from video computer terminals. Since users of these devices typically spend many hours daily in close proximity, they would be subject to chronic long-term exposures to any emitted radiation. Radiation was detected at frequencies ranging from 1.5 kHz to 1,420 MHz in the RF portion of the EM spectrum and from 350 nm to 600 nm in the ultraviolet and visible region. However, the levels were far less than the most restrictive permissible exposure levels established by any agency or government of any nation. There is no experimental or epidemiological evidence presently available to indicate that these levels of RF radiation have any deleterious effects on the human biological system.

Computers↗