PubMed Health⌕ Search

Biomedical subjects

R N Walker

Publications and source records attributed to R N Walker.

15 recordsLinked to original sources
PubMed1985

Passive movement of radioactive microspheres from bone and soft tissue in an extremity.

Bone biopsy is the definitive method for bone tumor diagnosis. Unfortunately, the procedure is not without risk and may substantially increase the rate and extent of tumor cell metastasis. This study used radioactive microspheres (15 micron diameter) to explore the spread of cell-sized particles from the distal femur into the lymphatic system, venous drainage, and local tissue following a simulated biopsy in the canine model procedure. In the initial group of test animals the microspheres rapidly moved from the femur through the venous system to the lungs. There was no movement from the femur into the lymphatic system within 4 days. The lungs effectively filtered the 15 micron microspheres, thus preventing arterial dissemination. Additional groups were used to explore the movement of the cell-sized particles from the soft tissue surrounding the bone. At the end of the 4 day experimental period, microspheres were found in the iliac lymph nodes in two of nine animals. Microspheres were not detected in the lungs of any of these nine animals. These results suggest that tumor cell-sized particles can move rapidly from the bone venous system to the lungs following a bone biopsy. It appears that the lymphatic system does not contribute to this rapid dissemination. However, the role of lymphatics in a more chronic process remains unclear.

Animals↗
PubMed1979

Free radical activation of N-hydroxy-2-acetylaminofluorene by methemoglobin and hydrogen peroxide.

We have shown that N-hydroxy-2-acetylaminofluorene, a metabolite of 2-acetylaminofluorene, is converted via a nitroxide free radical into N-acetylaminofluorene and 2-nitrosofluorene by H2O2 in the presence of methemoglobin. Utilizing optical methods, we have demonstrated that the rate of 2-nitrosofluorene production parallels that of N-hydroxy-2-acetylaminofluorene oxidation. This evidence is consistent with a model whereby two molecules of N-hydroxy-2-acetylaminofluorene yield two nitroxide free radicals which then dismutate to form one molecule of N-acetoxy-2-acetylaminofluorene and one molecule of 2-nitrosofluorene. The Km of N-hydroxy-2-acetylaminofluorene for this reaction is 114 microM with a Vmax of 50 microM/min.

2-Acetylaminofluorene↗
PubMed1976

Lipid hydroperoxide activation of N-hydroxy-N-acetylaminofluorene via a free radical route.

The data presented here demonstrate that linoleic acid hydroperoxide in the presence of methemoglobin or hematin activated the carcinogen N-hydroxy-N-acetyl-2-amino-fluorene via the nitroxyl free radical intermediate into 2-nitrosofluorene and N-acetoxy-N-acetyl-2-aminofluorene. Ascorbate inhibited the activation, in which case the free radical intermediate was replaced by the ascorbate free radical. On the basis of optical kinetics, we have established that the rate of linoleic acid hydroperoxide decrease paraleled the rate of N-hydroxy-N-acetyl-2-aminofluorene decrease and also the rate of 2-nitrosofluorene increase. The stoichiometry of the reaction was such that, for every 2 linoleic acid hydroperoxide molecules consumed, 2 N-hydroxy-N-acetyl-2-aminofluorene molecules were oxidized and 1 2-nitrosofluorene and 1 N-acetoxy-N-acetyl-2 aminofluorene molecule was formed.

Ascorbic Acid↗
PubMed1976

Body build and behavior in emotionally disturbed Dutch children.

Some physique-behavior relations were determined in 75 boys and 51 girls, aged 6 to 14, in a residential treatment center in Holland. Each child's behavior was rated by four group workers on a checklist yielding eight summary scores. Physique was judged from nude photographs for manifest endomorphy, mesomorphy, and ectomorphy. While a number of moderate-sized relations appeared in zero-order and multiple correlations, canonical analysis showed two significant, independent sets of relations between physique and behavior in the boys, one in the girls. Among the boys, one set related mesomorphy and energy level, the other related primarily ectomorphy with unsocialness, excitability, and cooperativeness. Among the girls, these same behaviors were compressed in a single set, primarily relating energy level but also unsocialness, excitability, and cooperativeness positively with mesomorphy and negatively with endomorphy and ectomorphy. Compared with findings on the same instrument in a sample of normal American preschoolers, many individual associations were similar, despite differences in culture and language, age, intelligence, social status, adjustment, and residential setting of the S's.

Adolescent↗
PubMedDate not supplied

Sheldon's trunk index and the growth of the thoracic and lumbar trunk.

The trunk index (TI), a ratio of the area of the thoracic trunk to that of the lumbar trunk, is measured on a somatotype photograph marked according to defined criteria. Photographs of 82 boys from the Harpenden Growth Study were measured at ages 5 to 18 years, in an order that obscured which photographs were of the same boy at different ages. Remeasurement two months later of 12 boys at each of ages 5, 11, and 18 years showed retest correlations of 0.97 or higher for thoracic and lumbar areas separately and of about 0.95 for their ratio. When 57 boys aged 17 to 20 years were measured by another worker, their TI values correlated 0.90 with those used in this study. Inter-age correlations among the unedited TI values were approximately 0.9 between ages a year apart and declined as age differences increased. Correlations with values at age 18 increased from about 0.7 at age 5 to 0.9 by age 16. Editing was done by remeasuring all values that deviated by more than 0.05 TI units from a regression line based on each subject's total array of values. In the edited data, correlations with TI values at age 18 increased, ranging from 0.8 at age 5 to 0.95 by age 16. Mean TI was quite stable, ranging only between 1.45 and 1.51 for the whole age span, with the lowest values appearing from 11 to 14 years. In 43 of the 59 boys whose series allowed determination of peak height velocity (PHV), a 'TI dip' appeared: one to three TI values fell more than 0.05 TI units below the boy's overall regression line shortly before PHV. Distance and velocity curves are given for growth of the thoracic and lumbar trunk areas. Peak velocity of growth of the lumbar area occurred on average a little earlier than that for the thoracic area; the TI dip was in part a result of this. Alterations of fat distribution as seen by skinfolds probably also contributed. Judging by their individual regression lines, about 80% of the boys showed no more than chance variation from a horizontal slope, their TI neither increasing nor decreasing overall. An additional 10% appeared to show significant slopes only because their series started or ended too near their TI dips. The remaining 10% of boys appeared to show real changes in TI as they grew. Examples of the most extreme changes are shown.

Adolescent↗
PubMedDate not supplied

Prediction of adult Sheldon somatotypes I and II from ratings and measurements at childhood ages.

The photographs of 82 boys from the Harpenden Growth Study were assigned somatotype ratings at ages 5, 8, 11, 14, and 18 years, using both Sheldon's earlier, anthroposcopic method and his revised, objective method (somatotype II). Inter-judge correlations for the anthroposcopic ratings of the 18-year-olds ranged from 0.79 to 0.93 for the three components; correlations for the somatotype II ratings ranged from 0.94 to 0.99. The three components of the somatotype II ratings showed greater independence of one another than did those of the anthroposcopic method, which tended to collapse towards two dimensions. Correlations for corresponding components between the anthroposcopic and somatotype II ratings at the same age were mostly in the low 0.80s. Mean somatotype ratings changed little with age in either method, but the somatotype II ratings were consistently higher in endomorphy and mesomorphy and lower in ectomorphy than the anthroposcopic ratings. Patterns of inter-age correlations were similar within methods: endomorphy showed lower age-to-age correlations than did mesomorphy and ectomorphy. Correlations of anthroposcopic component ratings with ratings at age 18 increased distinctly from age 5 to age 8, less sharply thereafter. Between ages 8 and 18, within observer, they were 0.72, 0.83, and 0.82, for endomorphy, mesomorphy, and ectomorphy. These 8-to-18 correlations for mesomorphy and ectomorphy are similar in magnitude to those for height.

Adolescent↗
PubMedDate not supplied

Stress fractures in skeletally immature patients.

Stress fractures are a common injury in an active population. As children become increasingly involved in organized sports, the recognition of stress fractures and differentiation from infections or neoplasms requires a knowledge of their most common sites, presentation, and clinical course. We retrospectively reviewed 34 stress fractures in 32 skeletally immature patients from June 1977 to May 1993. Age, fracture location, treatment, time to union or healing, associated conditions, complications, radiographs, and clinical outcome were recorded. Fifty percent of patients were involved in sports; the most common complaint was pain with activity. The most common site was the tibia (47%) followed by the fibula (21%) and femur (12%). All had resolution of symptoms and returned to normal activity. All but two healed with either activity modification or cast immobilization. The radiographic findings included early periosteal callus formation that rapidly consolidated to new bone on serial studies. A careful history, physical examination, and radiographs can help diagnose most common stress fractures in the skeletally immature individual and can differentiate stress fractures from infection or neoplasm with appropriate conservative treatment.

Adolescent↗