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Biomedical subjects

R D Hansen

Publications and source records attributed to R D Hansen.

At least 19 recordsLinked to original sources
PubMed2000

Total body protein in chronic diseases and in aging.

Substantial losses of total body protein (TBP) can occur in chronic diseases and in aging. Such losses impact negatively on immunity and quality of life, and on growth rates in children. Direct measurements of total body nitrogen (TBN) monitor the integrated changes in TBP over time and allow comparison with normal subjects. TBN assessment via neutron capture analysis is therefore the gold-standard method of TBP estimation, so that risk factors for protein deficit can be identified and patient management optimized. The nitrogen index (NI) can be used to predict prognostic outcome: an NI < 0.9 is associated with substantial wasting in HIV disease, an NI < 0.8 predicts significant pathophysiology in chronic renal failure, and a low NI is predictive of neutropenia in breast-cancer patients. These findings emphasize the central importance of adequate protein stores in recovery from disease or in maintaining quality of life. Aging appears to involve a gradual loss of TBP throughout adulthood. Cross-sectional data suggest that TBP declines curvilinearly with age, such that there is an accelerated decline after 65 years of age. However, longitudinal data are scarce, and little is known about the relative loss of visceral protein, as opposed to skeletal muscle protein. More clearly-defined data are essential if the effects of aging per se are to be separated from the effects of chronic disease. A further complication is the knowledge that physical activity also declines with age. Thus sarcopenia, the loss of skeletal muscle mass, could primarily result from disuse rather than aging. The economic impact of unsuccessful aging places a pressing need for multicompartment data in longitudinal study designs.

Adult↗
PubMed2000

Plasma sample preparation by ultrafiltration for FTIR analysis.

Total body water (TBW) may be significantly altered with disease. Isotope dilution techniques, considered to be the "gold standard" methods for measuring TBW, are expensive, time consuming and require considerable expertise, especially during the sample preparatory phase. In this study, a new method, ultrafiltration (UF), was hypothesised to be an efficient alternative to vacuum sublimation (VS) in the preparation of plasma samples for Fourier Transform Infra Red (FTIR) determination of TBW. Deuterium Oxide (D2O) concentrations were prepared in human plasma and subjected to both techniques. FTIR analysis was carried out on the resulting VS and UF solutions and on D2O concentrations in distilled water. The resulting absorbance values were then statistically compared. Urea concentrations prepared in D2O-containing plasma were also compared to "blank" plasma to investigate the effect of high plasma urea concentration on the resulting H2O/D2O mixture obtained during UF Paired t-tests showed that the VS plasma samples (p=0.003), but not the UF samples (p=0.9), were significantly different to D2O standards prepared in distilled water. While there was no evidence of an effect of urea on UF at low (0.4 g/L) D2O concentration, a marginal (p=0.04) effect occurred at a higher (1.6 g/L) D2O level. Throughput of samples was much more efficient with the UF technique. These findings indicate that the new UF method is an accurate, more efficient method of plasma sample preparation than the VS method in the FTIR determination of TBW.

Blood Chemical Analysis↗
PubMed1999

Determination of skeletal muscle and fat-free mass by nuclear and dual-energy x-ray absorptiometry methods in men and women aged 51-84 y (1-3).

BACKGROUND: Skeletal muscle mass (SMM) and fat-free mass (FFM) are important variables in nutritional studies. Accurate techniques for measuring these variables have not been thoroughly validated in elderly subjects. OBJECTIVES: The objectives of this study were to 1) compare SMM values derived from dual-energy X-ray absorptiometry (DXA) with those calculated by a nuclear method from total body potassium (TBK) and total body nitrogen (TBN) measurement (both: KN) in older subjects, and 2) assess the accuracy of FFM measurement by DXA in these subjects. DESIGN: TBK, TBN, DXA (model XR36; Norland, Fort Atkinson, WI), bioimpedance, and anthropometric measurements were performed on healthy women (n = 50) and men (n = 25) aged 51-84 y. RESULTS: Mean SMM by KN was not significantly different from SMM by DXA in either sex. SMM by KN predicted SMM by DXA with an SEE of 2.1 kg (r = 0.95, P < 0.0001 for women and men together). In the men, FFM by DXA agreed well with FFM estimated by TBK, skinfold thicknesses, bioimpedance analysis, and a multicompartment model. In women, FFM by DXA was 4-5 kg less than that by the other methods (P < 0.01). Truncal fat was related to intermethod FFM differences (r = 0.58, P < 0.0001). CONCLUSIONS: These data indicate that 1) either the nuclear or the DXA method can be applied to estimate SMM in healthy older subjects, and 2) the Norland DXA instrument significantly underestimates FFM in older women, in part, because of the influence of truncal adiposity.

Absorptiometry, Photon↗
PubMed1998

Murine in vivo total body nitrogen by photoactivation.

A facility to measure total body nitrogen (TBN) by photoactivation analysis in rats, using the 14N(gamma, n)13N reaction, was designed, calibrated and evaluated. TBN provides a quantitative estimate of nutritional status. TBN in humans can be measured by neutron activation, however the small absolute amount of nitrogen in rats causes difficulties with this technique. Photoactivation analysis involved irradiating the specimen with high energy photons from an 18 MV Medical Linear Accelerator to a dose of approximately 2 Gy. The technique was calibrated using urea solution rat phantoms with 2.0-3.0% nitrogen content. By analysing the measured decay curve, the initial nitrogen count rate of 0.51 MeV photons was determined and the initial oxygen count rate, being an interfering source of 0.51 MeV photons, was shown to be constant. Within the range of nitrogen concentrations studied, the response is linear (r2 = 0.9) with a CV of 3.5%. Thus, photoactivation provides a relatively simple, in vivo technique for determining total body nitrogen in rats.

Animals↗
PubMed1998

Detection of Staphylococcus aureus in milk by use of polymerase chain reaction analysis.

OBJECTIVE: To evaluate polymerase chain reaction (PCR) analysis for detection of Staphylococcus aureus (nuc gene) in fresh and formalin-preserved milk. SAMPLE POPULATION: Samples from 80 lactating sheep and 100 lactating dairy cows. PROCEDURE: 4 lactating sheep were inoculated with S aureus by intramammary infusion. A set of primers specific for the nuc gene of S aureus was used to develop a PCR technique, and modification of the rapid boil method was used to isolate bacterial DNA. Milk was obtained from experimentally infected sheep before and after infusion with S aureus, and from the 100 cows and remaining 76 sheep. Samples were screened by bacteriologic culture and PCR. To validate the PCR assay, S aureus or other pathogens were added to distilled water and "normal" sheep milk samples, with and without formalin. RESULTS: The PCR assay was 100% specific for S aureus when known negative and positive samples were tested. Sensitivity was 100% for samples with added S aureus or other pathogens. Sensitivity was lower for samples obtained from experimentally infected sheep, but increased from 53% to 90% with increased washing of target DNA. CONCLUSIONS: The PCR technique based on the nuc gene is able to detect S aureus in sheep milk yields results faster than does traditional culturing, is highly specific, and is able to detect S aureus in formalin-fixed milk samples. CLINICAL RELEVANCE: The assay is particularly suitable for analysis of samples shipped or stored without refrigeration. Although antibiotics in milk may inhibit growth in culture, they should not affect the results of the PCR assay.

Animals↗
PubMed1996

Infrared thermometry in the diagnosis and treatment of heat exhaustion.

Infrared (IR) thermometers (FirstTemp 2000A, Intelligent Medical Systems, California) were used to monitor tympanic temperature (Tty) in 12 collapsed fun-runners suspected of suffering exertion-induced heat exhaustion (EIHE). Rectal temperature (Tre) was monitored via digital clinical thermometers. Conditions during the fun-run and in the field treatment centre were cool (air temperature 16-18 degrees C, relative humidity 60-65%). On admission, Tty was (mean +/- SEM) 1.2 +/- 0.3 degrees C lower than Tre. For admission plus subsequent monitoring data pooled, although Tty correlated significantly with Tre (r = 0.86, p < 0.001), mean Tty (37.4 +/- 0.2 degrees C) was significantly lower (p < 0.01) than mean Tre (38.4 +/- 0.4 degrees C). Cotton wool ear pads, applied to 10 of the runners on admission to minimise environmental effects on Tty, did not significantly improve the IR monitoring. A Tty > or = 37.1 degrees C predicted a Tre > or = 38 degrees C (an established diagnostic criterion for EIHE) with a sensitivity of 0.93 and a specificity of 0.63. These data indicate that IR tympanic thermometry, when utilised in cool environments, can result in misdiagnosis of heat exhaustion. Although IR thermometry shows some promise as a rapid, non-invasive means of monitoring core temperature, it should not be used in the diagnosis and treatment of heat exhaustion unless further research validates the method.

Adult↗
PubMed1996

Calibration of a total body potassium monitor with an anthropomorphic phantom.

An anthropomorphic phantom was used to calibrate a supine geometry sodium iodide total body potassium monitor. Correction factors accommodating variability in subject size were empirically determined. Measurements on 12 males of weight 45-96 kg, height 161-184 cm and 18 females of weight 48-89 kg, height 153-175 cm, showed that the 40K calibration factor (F, counts s-1 (g of potassium)-1) was significantly correlated (r = 0.88, p < 0.0001) to subject (weight/height)0.5, indicating comparable accuracy to 42K-based calibration procedures. Fat-free mass determined from the potassium measurements of 16 subjects correlated significantly with fat-free mass estimated from skinfold thickness (r = 0.98, p < 0.0001), dual-energy x-ray absorptiometry (r = 0.99, p < 0.0001) and bioimpedance analysis (r = 0.98, p < 0.0001). These data, together with the precision (coefficient of variation, CV = 1.5%) and accuracy (CV = 4.5%) of the system, indicate that this calibration procedure represents a relatively low-cost, non-invasive alternative to 42K-based methods of calibrating total body potassium monitors.

Absorptiometry, Photon↗
PubMed1996

Infrared tympanic temperature as a predictor of rectal temperature in warm and hot conditions.

BACKGROUND: Infrared (IR) thermometry has been proposed as a rapid, non-invasive means of monitoring core temperature. However, it has not been validated for use in warm to hot environments. HYPOTHESIS: IR tympanic temperature (Tty) accurately predicts rectal temperature (Tre) during simulated marching in warm and hot conditions. METHODS: Tty, and thermistor-derived Tre, aural canal (Tac) and cheek skin (T cheek) temperatures were monitored in seven males during 100 min of treadmill walking, in combat uniforms, at 5 km.h-1, slope 6%, in warm (30 degrees C, 60% RH) and hot (40 degrees C, 30% RH) conditions. RESULTS: Tty was significantly different to Tre in hot, but not warm, conditions. Final Tty was 0.2 degrees C < Tre in warm, but 0.4 degrees C > Tre in hot, conditions. From 60-100 min of the warm trial, Tty predicted Tre with a standard error of estimate (SEE) of 0.15 degrees C (r = 0.9, p < 0.0001). In a multiple regression model, the combination of Tty, Tac, and Tcheek reduced this SEE to 0.1 degrees C. In the H trial, from 60-100 min Tty predicted Tre with a SEE of 0.21 degrees C (r = 0.7, p < 0.0001). Tty and Tac correlated significantly in both trials. CONCLUSIONS: (1) the IR method should provide useful estimates of Tre in the field provided the influence of ambient conditions is taken into account; (2) the IR method is not as reliable as rectal monitoring in distinguishing accurately between degrees of heat strain; and (3) Tre prediction with the IR device may be improved in warm conditions if skin temperatures are combined with Tty.

Adult↗
PubMed1994

Cultural, molecular, and immunological characterization of the etiologic agent for atypical canine ehrlichiosis.

More than 100 cases of canine ehrlichiosis, with three fatalities, were serologically negative by the indirect immunofluorescent antibody (IFA) test with Ehrlichia canis or E. sennetsu antigen but were reactive at titers of 10 to 640 with E. risticii. Ehrlichia-like agents were isolated from three such cases. The agents isolated from those cases were morphologically indistinguishable from each other and from a prototype, E. risticii, the etiologic agent of equine monocytic ehrlichiosis, in terms of growth characteristics and by light or electron microscopy. The patterns of and products from PCR were identical to those of E. risticii. The 16S rRNA sequences were distinct from those of E. canis and E. ewingii but were identical to those of E. risticii. A PCR product corresponding to the 5' half of the 16S rRNA gene was obtained from amplification of DNA from E. risticii and both sources of the atypical canine ehrlichiosis agent but was not obtained from uninfected host cells. The entire sequence of 719 nucleotides was identical for all three sources. The percentages of relatedness of the partial 16S rRNA gene of the atypical canine ehrlichiosis agent to E. risticii, E. sennetsu, E. platys, E. equi, E. phagocytophila, E. canis, E. chaffeensis, and E. ewingii were 100.0, 98.9, 83.7, 83.0, 83.0, 82.2, 81.8, and 81.5, respectively. These data are consistent with the identity of these isolates as E. risticii. The caninotropic characteristics of naturally acquired infections due to E. risticii are herein described for the first time, and the epizootiological implications are discussed in relation to the host range of E. risticii, which may include dogs as reservoirs.

Animals↗
PubMed1992

Serum haptoglobin concentration in swine naturally or experimentally infected with Actinobacillus pleuropneumoniae.

Serum haptoglobin (Hp) concentrations were measured in swine that were naturally or experimentally infected with Actinobacillus pleuropneumoniae. In swine from a specific-pathogen-free herd, mean serum concentration of Hp (+/- SD) was 5.79 +/- 1.06 mg of cyanmethemoglobin-binding capacity (CHBC)/dl. Serum Hp concentrations in paired samples were measured at 7-day intervals in 40 swine randomly selected from a conventional herd that was experiencing an acute episode of pneumonia and deaths caused by A pleuropneumoniae serotype-5 infection. Day-0 and -7 serum Hp concentrations were 24.58 +/- 1.38 and 23.10 +/- 1.12 mg of CHBC/dl, respectively, with no significant difference between these measurements. In a second conventional herd with a history of chronic infection with A pleuropneumoniae serotype 5, serum concentrations of Hp measured in paired samples obtained 6 days apart were 12.36 +/- 0.81 and 18.63 +/- 0.76 mg of CHBC/dl, respectively, and were significantly (P < 0.05) different from each other. Twenty-nine 12-week-old conventional swine were challenged intranasally with A pleuropneumoniae serotype 1 (n = 19) and serotype 5 (n = 10). Serum Hp concentration increased from prechallenge concentrations of 7.49 +/- 1.38 and 15.10 +/- 1.22 mg of CHBC/dl, respectively, to 41.01 +/- 1.35 and 22.37 +/- 1.78 mg of CHBC/dl, respectively, 72 hours after challenge. For these 29 swine, serum Hp concentration was positively correlated with rectal temperature (r = 0.34; P < 0.001) during the immediate postchallenge period.

Actinobacillus Infections↗
PubMed1992

Repression at encoding: discrete appraisals of emotional stimuli.

In previous research, the emotions associated with repressors' memorial representations were found to be more discrete than those associated with nonrepressors'. In each of the 3 experiments reported here, repressive discreteness was apparent in repressors' appraisals of emotional stimuli at the time they were encoded. In 1 experiment, Ss appraised individual facial expressions of emotion. Repressors judged the dominant emotions in these faces as no less intense than did nonrepressors, but they appraised the blend of nondominant emotions as less intense than did nonrepressors. In the remaining 2 experiments, Ss appraised crowds of emotional faces as well as crowds of geometric shapes. In both crowd experiments, the repressive discreteness was evident in appraisals of crowds of emotional faces but not in appraisals of crowds of geometric shapes. The repressive discreteness effect did not appear to reflect a general repressor-nonrepressor difference in the appraisal of stimulus features. Rather, the results suggested that repressive discreteness may be constrained to appraisals of emotions.

Adaptation, Psychological↗
PubMed1988

Finding the face in the crowd: an anger superiority effect.

Facial gestures have been given an increasingly critical role in models of emotion. The biological significance of interindividual transmission of emotional signals is a pivotal assumption for placing the face in a central position in these models. This assumption invited a logical corollary, examined in this article: Face-processing should be highly efficient. Three experiments documented an asymmetry in the processing of emotionally discrepant faces embedded in crowds. The results suggested that threatening faces pop out of crowds, perhaps as a result of a preattentive, parallel search for signals of direct threat.

Anger↗
PubMed1988

Repression of emotionally tagged memories: the architecture of less complex emotions.

We asked subjects to recall memories of events that evoked feelings of anger, sadness, fear, and embarrassment. These memories evoked patterns of dominant and nondominant emotions. The dominant emotions evoked by the recalled events were no less intense for repressors than nonrepressors, but repressors' patterns of nondominant emotions were less intense than those of nonrepressors. The data suggested that for repressors the associative network of negative emotional memories may be more discrete and less complex than that for nonrepressors. This finding was consistent with recent research indicating that negative emotional memories are less accessible for repressors than for nonrepressors. The pattern of multivariate effects suggests that this repressive memorial architecture may serve the motive of isolating fear-associated memories.

Adaptation, Psychological↗