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Biomedical subjects

D Carlson

Publications and source records attributed to D Carlson.

At least 19 recordsLinked to original sources
PubMed1990

The Caltrac accelerometer as a physical activity monitor for school-age children.

The performance of the Caltrac accelerometer was studied in elementary school-age children under field and laboratory conditions. In Study 1, 35 children (20 boys, 15 girls, mean age = 10.8 yr) wore the accelerometer and a heart rate (HR) monitor for 2 d. Caltrac activity counts per hour were compared to the mean "activity HR", which was calculated by subtracting the mean of the five lowest HRs of the day from each recorded HR. Pearson r's between accelerometer and activity HR were 0.54 (P less than 0.001) on day 1 and 0.42 (P less than 0.02) on day 2. Inter-instrument reliability in the field was r = 0.96. Both accelerometer and HR data were significantly correlated with physical activity recalls of the same day. In Study 2, 15 children walked/ran for 10 min at 3, 4, and 5 mph on a horizontal treadmill while wearing two accelerometers. Oxygen uptake was directly measured each minute. Reliability of the Caltracs in the laboratory was 0.89. Activity count correlated r = 0.82 (SEE = 23%) with net calorie cost per kg of body weight. Net caloric expenditure per kg of weight was 0.101 kcal.kg-1.d-1 per Caltrac activity count. These data support the use of the Caltrac accelerometer as a physical activity measure for school-age children, and the objective data tended to corroborate the children's short-term activity recalls.

Adolescent↗
PubMed1989

Data acquisition and processing system for drug release characterization by thin layer chromatography.

Samples of an antibiotic released from an ocular insert in an in vitro test are characterized by thin layer chromatography (TLC). Conventional characterization methods include cutting and weighing strip chart paper peak profiles obtained with a scanning densitometer for spotted TLC plates, and relating peaks for unknowns to peaks for standards on the basis of relative weights. A data collection and processing system is described in which the data collection and processing is highly automated utilizing a specially developed software program. A Kontes densitometer (Model 800) and a personal computer (IBM PC-AT or Zenith-248) are interfaced using a Keithley 570 data acquisition system. Two BASIC software programs were developed to provide quantitative evaluation of chromatograms of an antibiotic (tylosin tartrate); the first program generates chromatograms on the computer screen through initiating controlled operation of a scanning densitometer for TLC plate analysis, and the second program processes the data providing quantitative analysis of the spectral output through a peak detection and peak integration routine. The approach represents a new general, versatile, quick and effective method to characterize TLC samples for various numbers of peaks for unknowns and standards for different concentration levels.

Chromatography, Thin Layer↗
PubMed1987

Urinary and hematologic indexes of hypohydration.

As part of a large-scale field feeding system test we were able to collect and study hundreds of aliquots of overnight urine samples obtained immediately prior to a fasting blood sample on days 1, 20, and 44 of the field test. The large number of experimental samples (greater than 650) and concomitant collection of blood and urine aliquots along with data on body weights gave us the opportunity to assess and quantitate the sensitivity of commonly used criteria of hypohydration. Urine aliquots for all test days were initially categorized by specific gravity (SG) greater than or equal to 1.03 (n = 124) or less than 1.03 (n = 540). Creatinine levels were elevated (P less than 0.001) in the concentrated urine samples, but a decreased trend in sodium-to-potassium ratios in these samples failed to achieve statistical significance (P greater than 0.05). However, when individuals with high SG urine were subclassified by a criterion of weight loss greater than 3% from original body weight, then creatinine concentrations were elevated (P = 0.05), whereas sodium-to-potassium ratios were decreased (P = 0.05) when subjects also with high SG but weight loss less than 3% were compared. Because of the moderate altitude (2,000 m) of the field site and the time of sojourn (44 days), there occurred a slight, but significant (P less than 0.001), erythropoietic response. Hematocrit and serum osmolality were not significantly different when examined by the criteria of high or low SG urine and weight loss greater than or less than 3% original body weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Urea Nitrogen↗
PubMed1985

A biotin-avidin enzyme immunoassay for the quantitation of serum ferritin.

A biotin-avidin enzyme immunoassay (EIA) for measurement of ferritin in human serum is described. This procedure involves the use of specific antibody immobilized on beads, biotin-labeled specific antibody and enzyme-labeled avidin. Reproducible results were achieved within 2 h for ferritin in serum in the range of 5-500 ng/ml. Ferritin levels as low as 0.1 ng/ml can be measured. The biotin-avidin EIA, a radioimmunoassay kit, and an EIA kit were used to determine serum ferritin levels in healthy adults. Good agreement was found between the biotin-avidin EIA and the other methods.

Avidin↗
PubMed1984

SES-related aspects of neuropsychological performance.

Children from different socioeconomic backgrounds have been observed to employ different cognitive styles in problem-solving situations. These cognitive styles have in turn been linked to the functional specialization of the cerebral hemispheres. It was hypothesized, therefore, that performance asymmetries would also be SES-related, high-SES children processing stimuli presented to the right visual field-left hemisphere (RVF-LH) more efficiently than those presented to the left visual field-right hemisphere (LVF-RH) and low-SES children showing the reverse pattern. A laterality task was administered tachistoscopically to 120 children, divided evenly by SES (high and low), sex, and grade (fifth and seventh). A marked RVF-LH advantage emerged among the high-SES group and a weak LVF-RH advantage among the low-SES group. Thus, the results provided general support for the central hypothesis. The findings are reviewed in the context of current models of human information processing in the cerebral hemispheres, and their broader implications for understanding SES-related differences in cognitive function are discussed.

Child↗
PubMed1982

Effect of interstitial fluid (kerosene) on pressure-volume characteristics of rat lung.

Although pulmonary interstitial edema has been estimated to decrease pulmonary compliance (CL), it has been experimentally difficult to demonstrate whether the observed changes in CL are directly due to the presence of interstitial fluid or if they result instead from concomitant pulmonary vascular engorgement and/or alveolar edema. Since kerosene-inflated lungs do not leak, we were able to use kerosene to measure the effect on CL of the accumulation of interstitial fluid (kerosene) in the postmortem rat lung. Pressure-volume (PV) studies of the lung were done during the progressive increase in interstitial fluid (kerosene). Analysis of the deflation limbs of the quasistatic PV curves obtained following serial inflations with kerosene indicated that the maximal volume of kerosene [MV35, equal to the maximum tissue plus airway volume at a transpulmonary pressure (Ptp) of 35 cmH2O] was 3.8 +/- 1.2 ml (31.0 +/- 11.8%) greater than TLC35 [air volume at Ptp of 35 cmH2O prior to kerosene inflation]. The increases in interstitial kerosene volume had no effect on kerosene PV characteristics, as was demonstrated by superimposing lung PV curves obtained at various states of interstitial filling. We conclude that the interstitial compartment is large and very compliant and that the presence of even great amounts of fluid limited to this compartment does not restrict lung expansion.

Animals↗
PubMed1982

Developmental and differential aspects of mental rotation in early adolescence.

A chronometric mental rotation paradigm was applied to examine manipulation of visual imagery in early adolescence in relation to age, sex, mental rotation ability (measured psychometrically), and socioeconomic background. Fifth- and seventh-grade boys and girls from middle and lower socioeconomic backgrounds viewed tachistiscopically letters of the alphabet presented at 0 degrees, 60 degrees, 120 degrees, and 180 degrees of rotation and were asked to judge whether the letter was forward or backward. In one condition, children were given no information about the test letter, and in the other, advance visual information about its identity and orientation was provided. With age, children became more skillful at rotating and were more likely to show evidence of using the advance information as a visual image. There were no sex differences. Socioeconomic differences were more pronounced in the fifth than the seventh grade. Children showing high mental rotation ability were more likely than low-ability children to show evidence of rotating visual stimuli on the chronometric measure. The findings are discussed in terms of adolescent cognitive development.

Age Factors↗
PubMed1981

Metabolic contribution of CO2 to the "group effect".

Metabolic rates (VCO2) were determined in 22 mice. Subsequently 11 of the mice were placed into separate metabolic chambers. Each chamber was connected to one other metabolic chamber containing one mouse. The metabolic rates of the 11 "donor" and the 11 "'recipient" mice were measured. Afterwards the direction of airflow was reversed so that the previous donor became the recipient mouse and the previous recipient became the donor. Again VCO2 was measured. When the mice were donors, VCO2 = 2.75 +/- 1.0 ml CO2 . g-1 . h-1, whereas when recipients, VCO2 = 1.9 +/- 1.0 ml CO2 . g-1 . h-1 (P less than 0.01). Eleven of the mice were then made anosmic using an intranasal instillation of 5% ZnSO4. Anosmia was confirmed behaviorally. The metabolic rates of the anosmic and control mice were again determined when each was a donor and a recipient. VCO2 dropped from 3.1 to 1.8 ml CO2 . g-1 . h-1 from donor status to recipient status. Finally, VCO2 was determined when all 22 mice were exposed to 0.05% CO2 or 0.2% CO2 in air (the level of CO2 in the exhaust air of donor mice). VCO2 dropped from 3.0 +/- 0.38 on 0.05% CO2 to 1.7 +/- 1.01 on 1.01 ml CO2 . g-1 . h-1 on 0.2% CO2 in the anosmic group and from 2.9 +/- 0.29 to 1.91 +/- 0.51 ml CO2 . g-1 . h-1 in the control group when exposed to the same gases. These experiments suggest that the airborne factor emanating from the donor chambers was acting systematically and not via the olfactory system. This factor may be a low level of CO2.

Animals↗
PubMed1979

Early changes in muscle glucose-6-phosphate dehydrogenase activity after denervation: locus and dependence on nerve stump length.

Glucose-6-phosphate dehydrogenase (G6PD) activity of rat diaphragm muscle increased significantly 12 h after intrathoracic ('distal') denervation. Since this change represented one of the earliest known events after loss of innervation, the mechanism of neuronal regulation and the nature of the muscle response were further investigated. When, instead of distal denervation, the motor nerve was cut about 3.5 cm from the diaphragm, G6PD activity slightly decreased 12 h later. Denervations in which part of the same hemidiaphragm had a short nerve stump and another part, a long nerve stump, also showed a differential increase of G6PD activity dependent on length of nerve stump. In biochemical studies of the locus of the early post-denervation elevation of G6PD, enzyme activity was increased both in endplate and non-endplate regions of the muscle. Finally, the histochemical reaction for G6PD was more intense in both muscle fibers and interstitial elements, although the former made the major contribution to the biochemical results. In sum, muscle G6PD enzyme activity is closely regulated by a neurotrophic mechanism partly independent of nerve or muscle electrical activity.

Animals↗
PubMed1979

Membrane specializations in the peripheral retina of the housefly Musca domestica L.

Membrane specializations of the peripheral retina of the housefly (Musca domestica) are revealed in thin sections and freeze fracture/etch replicas. Septate junctions are abundant in corner areas of the pseudocone enclosure bonding: between homologous corneal pigment cells (CPC); between homologous large pigment cells (LPC); between CPC-LPC; between Semper cells (SC); between SC-CPC. Spot desmosomes are present between Semper cells. It is likely that septate junctions function as strengthening adhesions in this area. A new membrane specialization similar to a continuous junction was observed between retinular cells of the same or adjacent ommatidium. This junction has indistinct septa in the 115 A intermembrane cleft and is intermittent in character. When this junction is absent, the apposed cells gape apart. In freeze fracture studies, this junction is characterized by bridges composed of fused membrane particles and randomly arranged particles on the P face, and noncorresponding grooves on the E face. The ridges are elongate and roughly parallel and sometimes they form enclosures. Mitochondria line up along these junctions, often within 90 A of the unit membrane. This membrane specialization has characteristics of tight and continuous junctions. In line with previous findings, we suggest that this junction assists in retinular cell orientation, possibly in enforcing the ommatidial twist and in maintaining localized ionic concentration gradients between retinular cells.

Animals↗
PubMed1979

Perceptions of fatigue as related to alcohol ingestion.

An experiment is reported in which the role of alcohol in the emergence of fatigue was studied. Eleven (11) participants were requested to operate a driver trainer until they found the task too adverse to continue under conditions of high blood alcohol (BACL greater than 0.08%), low blood alcohol (BACL less than 0.08%), and no blood alcohol. Skill and heart rate were monitored and any personal distresses or observations made about performance were reported to an experimenter who acted in the role of 'passenger'. Results show decline in endurance as blood alcohol increases, but that a higher level of personal distress is endured by drivers who have imbibed, as compared to those who have not. Systematic discrepancies occur between the impressions gained by the experimenter (passenger) from verbal reports made by the driver, and the kinds of self-ratings drivers provide. Features of fatigue are analyzed theoretically as perceptual phenomena as related to alcohol and accidents.

Alcohol Drinking↗
PubMed1978

Benign multilocal cystic nephroma.

Three cases of multilocular cystic nephroma are described. This entity differs from congenital multicystic kidney and adult polycystic disease in that it involves only a segment of one kidney. While the excretory urogram, nephrotomogram, and arteriogram show the lesion to be primarily avascular, the two cases studied by ultrasound were predominantly solid. This finding is felt to relate to the small size of the cysts as well as the presence of some solid primitive components. Because it is difficult to differentiate this lesion from an avascular renal carcinoma, surgical biopsy should be considered to help avoid a needless nephrectomy.

Adult↗
PubMed1978

Impact of age integration on the well-being of elderly tenants in public housing.

The social, psychological, and environmental situations of a national area probability sample of 1875 elderly tenants in 153 public housing sites were studied by means of interviews with tenants and project mangers and direct observation of social and environmental characteristics of the housing. In this report the association between the age mix of the housing and the well-being of the tenants was investigated. With a variety of personal, social, and physical environmental characteristics statistically controlled, age segregation showed small but reliable relationships to on-site activity participation, morale, housing satisfaction, and neighborhood motility. The results are discussed in terms of policy and planning designed to maximize options for the individual.

Age Factors↗