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Biomedical subjects

R K Johnson

Publications and source records attributed to R K Johnson.

At least 73 records · Page 4Linked to original sources
PubMed1998

Developmental changes in energy expenditure and physical activity in children: evidence for a decline in physical activity in girls before puberty.

OBJECTIVE: To examine individual changes in energy expenditure and physical activity during prepubertal growth in boys and girls. METHODS: Total energy expenditure (TEE), resting energy expenditure, physical activity-related energy expenditure, reported physical activity, and fat and fat-free mass were measured three times over 5 years in 11 boys (5.3 +/- 0.9 years at baseline) and 11 girls (5.5 +/- 0.9 years at baseline). RESULTS: Four-year increases in fat ( approximately 6 kg) and fat-free mass ( approximately 10 kg) and resting energy expenditure ( approximately 200 kcal/day) were similar in boys and girls. In boys, TEE increased at each measurement year, whereas in girls, there was an initial increase from age 5.5 (1365 +/- 330 kcal/day) to age 6.5 (1815 +/- 392 kcal/day); however, by age 9.5, TEE was reduced significantly (1608 +/- 284 kcal/day) with no change in energy intake. The gender difference in TEE changes over time was explained by a 50% reduction in physical activity (kcal/day and hours/week) in girls between the ages of 6.5 and 9.5. CONCLUSIONS: These data suggest a gender dimorphism in the developmental changes in energy expenditure before adolescence, with a conservation of energy use in girls achieved through a marked reduction in physical activity.

Basal Metabolism↗
PubMed1998

Genetics of the interval from weaning to estrus in first-litter sows: correlated responses.

The objective of this study was to evaluate relationships between rebreeding performance and growth performance (n = 3,777 gilts) and rebreeding performance and reproductive performance (n = 2,242 sows). Our data were from a selection experiment for shorter intervals from weaning to estrus after the first parity (IWE), involving Dutch Landrace pigs, in which a selection line and a control line without selection were maintained for eight generations. Relationships were evaluated before and after transforming IWE to normal interval (NI; IWE < or = 7 d), prolonged interval (PI; IWE > 7 d), and incidence of a prolonged interval (INC). Heritabilities of NI, PI, and INC were .18, .17, and .27. Within-line phenotypic and genetic trends in growth and reproductive performance were not different from zero and did not diverge as a correlated response to the selection applied. Phenotypic correlations between IWE, NI, or PI and growth or reproductive performance were low and ranged from -.14 to .11. Genetic correlations were higher, and, for the majority of traits, the genetic correlations with NI and PI had a different sign. Phenotypic and genetic contrasts between sows with NI and sows with PI different from zero indicated that INC may increase as a correlated response to selection for reproductive performance. Analyses using untransformed IWE or data from populations selected for rebreeding performance may underestimate the correlated response in IWE due to selection on economically important traits.

Animals↗
PubMed1998

Probenecid alters topotecan systemic and renal disposition by inhibiting renal tubular secretion.

Topotecan is primarily eliminated by the kidneys, with 60 to 70% of the dose recovered as topotecan total in the urine. To elucidate the mechanisms of topotecan renal clearance, we evaluated the effect of probenecid on topotecan renal and systemic disposition in mice. Topotecan lactone or hydroxy acid (1.25 mg/kg i.v.) was administered alone or in combination with probenecid (600 or 1,200 mg/kg) given by oral gavage 30 min before and 3 hr after topotecan. Serial blood samples (three mice per time point) and urine samples (five mice per treatment arm) were collected during a 6-hr period. Compared with topotecan alone, coadministration of topotecan lactone or hydroxy acid with probenecid (600 mg/kg) decreased topotecan lactone, total, and hydroxy acid systemic clearance, and total renal clearance. The predominant effect of probenecid was to increase hydroxy acid area under the plasma concentration time curve after administration of topotecan lactone (238.8 vs. 109.9 ng.hr/ml alone, P < .05), or hydroxy acid (1297.2 vs. 355.0 ng.hr/ml alone, P < .05). By inhibiting renal tubular secretion, probenecid decreased renal and systemic clearance which led to an increase in topotecan systemic exposure. These data suggest that probenecid primarily inhibited secretion of the anionic hydroxy acid form, and by direct or indirect mechanisms increased topotecan lactone systemic exposure. Topotecan elimination through renal tubular secretion may have clinical relevance for the use of topotecan in patients with altered renal function.

Animals↗
PubMed1997

Total energy expenditure in adults with cerebral palsy as assessed by doubly labeled water.

OBJECTIVES: To characterize total energy expenditure (TEE) in free-living adults with cerebral palsy (CP) using the doubly labeled water technique, and to determine those physiologic variables and characteristics of CP that were markers of TEE in adults with CP. DESIGN: TEE was measured using the doubly labeled water technique in 30 free-living adults with CP (12 women, 18 men). To determine the best markers of TEE, the following factors were examined: CP status, resting metabolic rate (RMR), anthropometric characteristics and body composition by means of dual-energy x-ray absorptiometry (DXA) and skinfold thickness measurements, energy cost of leisure-time activities, and oral-motor impairment. STATISTICAL ANALYSIS: Means +/- standard deviations, t tests, Pearson product-moment correlation coefficients, Spearman rank correlation coefficients, chi 2, stepwise multiple-correlation regression analysis, and analysis of covariance were used to examine the relationships among variables of interest. RESULTS: TEE was highly variable in the sample (mean = 2,455 +/- 622 kcal/day for men and 1,986 +/- 363 kcal/day for women). Stepwise regression analysis showed that TEE was best predicted in the sample by RMR, percentage body fat determined by DXA, ambulation status, and sex (multiple R = .68, P = .003). When practical, easily measured variables were used, TEE was best predicted by height, ambulation status, percentage body fat by skinfold thickness measurements, and sex (multiple R = .61, P. = 018). The contribution of energy expended in physical activity to TEE was significantly higher in the ambulatory subjects than the nonambulatory subjects (25% vs 16%, respectively; P = .009). APPLICATIONS: The high degree of variability in TEE, largely attributable to high interindividual variation in energy expended in physical activity, makes it difficult to provide general guidelines for energy requirements for adults with CP. Because ambulation status was an important predictor of TEE, it must be accounted for in estimating energy requirements in this population.

Absorptiometry, Photon↗
PubMed1997

Two new nitrogenous sesquiterpenes from the sponge Axinyssa aplysinoides.

Bioassay-guided fractionation of the EtOAc extract of the Palauan sponge Axinyssa aplysinoides yielded two novel alkaloids, 1 and 2. The structure of 2-(formylamino)trachyopsane (1) was determined by X-ray analysis; and the structure of N-phenethyl-N'-2-trachyopsanylurea (2), by interpretation of the spectral data.

Antimutagenic Agents↗
PubMed1997

Rigidone, a sesquiterpene o-quinone from the gorgonian Pseudopterogorgia rigida.

As part of a search for novel biologically active compounds in the Macrophage Scavenger Receptor (MSR) assay, the EtOAc extract of a gorgonian coral, Pseudopterogorgia rigida, was shown to be active. Bioassay-guided fractionation of the extract yielded curcuphenol, curcuhydroquinone, curcuquinone, and a novel o-quinone, rigidone (1). The structure and stereochemistry of 1 was determined by interpretation of spectral data and chemical transformation.

Animals↗
PubMed1997

Daleformis, a new phytoalexin from the roots fo Dalea filiciformis: an inhibitor of endothelin converting enzyme.

As part of a search for novel inhibitors of endothelin converting enzyme (ECE), the MeOH-CH2Cl2 extract of the roots of Dalea filiciformis was shown to be active. Bioassay-guided fractionation of the extract yielded a novel phytoalexin, daleformis (1), whose structure was determined by interpretation of spectral data and X-ray analysis. Daleformis (1) inhibited ECE with an IC50 of 9 microM.

Acetylation↗
PubMed1997

Three new pseudodistomins, piperidine alkaloids from the ascidian Pseudodistoma megalarva.

Bioassay-guided fractionation of the MeOH-CH2Cl2 extract of the Micronesian ascidian Pseudodistoma megalarva yielded three new piperidine alkaloids, pseudodistomins D-F (3-5) and the previously reported pseudodistomins B and C (1 and 2). The structure and stereochemistry of these compounds were established by interpretation of spectral data. Pseudodistomins B-F were found to be active in a cell-based assay for DNA damage induction, but the activity was due to an alternative mechanism.

Alkaloids↗
PubMed1997

Bioactive and other sesquiterpenes from Chiloscyphus rivularis.

Bioassay-directed fractionation of the methyl ethyl ketone extract of Chiloscyphus rivularis yielded five new sesquiterpenes, 12-hydroxychiloscyphone (2), chiloscypha-2,7-dione (3), 12-hydroxychiloscypha-2,7-dione (4), chiloscypha-2,7,9-trione (5), and rivulalactone (6) in addition to the known sesquiterpenes, 4-hydroxyoppositan-7-one (7), chiloscyphone (1), and isointermedeol (8). The structure and stereochemistry of rivulalactone, a novel trinorsesquiterpene, was confirmed by its synthesis starting from 1. Compound 2 showed selective bioactivity in our yeast-based DNA-damaging assay and cytotoxicity to human lung carcinoma cells.

Antineoplastic Agents, Phytogenic↗
PubMed1997

Body composition in adults with cerebral palsy by dual-energy X-ray absorptiometry, bioelectrical impedance analysis, and skinfold anthropometry compared with the 18O isotope-dilution technique.

The aim of this study was to determine in adults with cerebral palsy the accuracy and practicality of standard methods used to estimate body composition. The sample consisted of 20 adults (13 men and 7 women) aged 20-55 y with various degrees of cerebral palsy. Percentage body fat was estimated from skinfold thickness, bioelectrical impedance analysis (BIA), and dual-energy X-ray absorptiometry (DXA), and compared with the reference measure of percentage body fat from total body water by 18O dilution. Values derived from use of BIA and skinfold thickness, estimated by using the Jackson-Pollock equation, were significantly different from those derived with use of 18O dilution (P < 0.001 and P < 0.001, respectively). There was no significant difference between percentage body fat measured with DXA and that measured with 18O. There was favorable agreement between DXA and 18O (mean difference: 0.06 +/- 9.6%), but not between skinfold thickness (mean difference: 6.33 +/- 12.3%) or BIA (mean difference: -6.55 +/- 13.6%) and 18O. Although DXA was the best measure for predicting percentage body fat in the sample, its high cost prohibits its use as a practical method. The best-fitting regression equation specific for this sample by using anthropometric measures to predict percentage body fat was as follows: 8.76 - (7.34 x sex) + (0.32 x weight) + (0.38 x biceps skinfold) (R2 = 0.84, P < 0.001, SEE = 4.85). This equation needs to be cross-validated in an independent sample of adults with cerebral palsy.

Absorptiometry, Photon↗
PubMed1997

Evidence for quantitative trait loci affecting ovulation rate in pigs.

Fifty-five microsatellite markers were scored in an F2 population of pigs (n = 114 females) developed at the University of Nebraska. The population was produced by crossing a line previously selected for 10 generations using an index of ovulation rate and embryonal survival and a line selected at random. The lines were from a common base population and differed by 6.7 ovulations and 3.1 fetuses at 50 d of gestation. Ovulation rate and number of fully formed and mummified pigs were recorded for each female. Data were analyzed with regression models that included random animal effects. Likelihood-ratio tests were used to test for quantitative trait loci (QTL) effects by deviating the log-likelihood for the full model that included additive and dominance QTL effects from the log-likelihood for the reduced model that did not contain QTL effects. A QTL for ovulation rate was found on chromosome 8 (P < .001) with an additive effect of 3.07 ovulations. Other evidence of potential QTL affecting ovulation rate was found on chromosomes 4 (P < .10), 13, and 15 (P < .05). Effects on chromosomes 4, 13 and 15 were not significant for fan experiment-wise threshold value of P < .001. No significant QTL for litter size or number of mummified pigs were found. Additional data are needed to confirm the location and the effect of QTL found for ovulation rate before markers associated with them can be used in marker-assisted selection.

Alleles↗
PubMed1996

Athetosis increases resting metabolic rate in adults with cerebral palsy.

OBJECTIVES: To determine whether resting metabolic rate (RMR) is higher or lower in adults with cerebral palsy compared with the RMR of control subjects and to further examine physical characteristics of cerebral palsy that might affect RMR. DESIGN: Twenty-one adults with cerebral palsy (9 women, 12 men) were compared with 50 control subjects (25 men, 25 women) within the same age range (18 through 50 years). The following measurements were made: RMR by indirect calorimetry, anthropometrics, body composition, and habitual physical activity patterns. The study was conducted at the University of Vermont General Clinical Research Center and the Ball State University Human Performance Laboratory. STATISTICAL ANALYSES: Mean values +/- standard deviations, t tests, Pearson product-moment correlation coefficients, analysis of covariance, and stepwise multiple correlation regression analysis were used to examine the relationships among variables of interest. RESULTS: No significant differences were found in body weight, body mass index, fat mass, percentage body fat, and measured RMR between the two groups. The subjects with cerebral palsy were significantly shorter, had less fat-free mass, and expended fewer kilocalories in leisure time activities than the control subjects. After statistical adjustment for differences in fat-free mass, the subjects with cerebral palsy had a 14% (P < .001) higher adjusted RMR (1,742 kcal/day) compared with that of the control subjects (1,534 kcal/day). According to stepwise regression analysis, RMR was best predicted in the entire sample by fat-free mass and the presence or absence of athetosis (multiple R = .83, P < .001). The presence of cerebral palsy alone was not significantly correlated with RMR. CONCLUSIONS: The increased energy requirements of adults with cerebral palsy can be partially explained by athetotic movements. In this sample, the presence of athetosis increased RMR by an average of 524 kcal/day.

Adolescent↗
PubMed1996

Comparison of multiple-pass 24-hour recall estimates of energy intake with total energy expenditure determined by the doubly labeled water method in young children.

OBJECTIVE: This study determined the accuracy of the multiple-pass 24-hour recall method for estimating energy intake in young children by comparing it with measurements of total energy expenditure made using the doubly labeled water method. DESIGN: Three multiple-pass 24-hour recalls were obtained over a 14-day period to estimate mean energy intake. Total energy expenditure was measured over the same 14-day period under free-living conditions using the doubly labeled water technique. SUBJECTS/SETTING: Twenty-four children between the ages of 4 and 7 years were tested at the General Clinical Research Center/Sims Obesity Nutrition Research Center at the University of Vermont. STATISTICAL ANALYSIS: t Tests, paired t tests, Pearson product-moment correlation coefficients, pairwise comparison to show relative bias and limits of agreement, and regression analysis were used to test the relationships among study variables. RESULTS: No difference was found between 3-day mean energy intake and total energy expenditure for the group (t = 2.07, P = .65). The correlation between individual measures of energy intake and total energy expenditure was not statistically significant (r = .25, P = .24). CONCLUSIONS: Data from 3 days of multiple-pass 24-hour recalls were sufficient to make valid group estimates of energy intake. The method was not precise for individual measurements of energy intake.

Body Composition↗
PubMed1996

The Albany Medical College Ventilator Walker.

This report describes the design and use of a wheeled walker that can accommodate a ventilator and oxygen tanks. It is constructed of aluminum tubing. The front of the walker has receptacles to support a Mark 7 Bird Ventilator and oxygen tanks. The back end of the walker has a bench seat that is lifted to allow entry into the walker. The seat provides rigidity and stability to the frame of the walker. The walker has been used in the Medical Intensive Care Unit of the Albany Medical Center to facilitate early ambulation of patients who are ventilator dependent or who require a portable source of oxygen to begin ambulation training.

Aged↗
PubMed1996

Plakortides, novel cyclic peroxides from the sponge Plakortis halichondrioides: activators of cardiac SR-CA(2+)-pumping ATPase.

As part of a search for novel activators of Ca2+ pumping activity of cardiac SR- (sarcoplasmic reticulum), the EtOAc extract of the Jamaican sponge Plakortis halichondrioides was shown to be active. Bioassay-guided fractionation of the extract followed by preparative TLC and HPLC yielded several known and novel compounds. Three of the novel cyclic peroxides, plakortides F, G, and H (3, 4, and 5) are the subject of this report. Their structures including relative stereochemistry were established by interpretation of spectral data. Micromolar concentrations of plakortides F-H (3-5) were found to significantly enhance Ca2+ uptake by SR.

Animals↗
PubMed1996

Halistanol disulfate B, a novel sulfated sterol from the sponge Pachastrella sp.: inhibitor of endothelin converting enzyme.

As part of a search for novel inhibitors of endothelin converting enzyme (ECE), the MeOH extract of a South African sponge, Pachastrella sp., was shown to be active. Bioassay-guided fractionation of the extract yielded a novel sterol sulfate, halistanol disulfate B (1). The structure and stereochemistry of 1 was established mainly by interpretation of spectral data. Disulfate (1) was found to be active at a micromolar concentration in the ECE assay.

Animals↗
PubMed1996

Fat intake and adiposity in children of lean and obese parents.

We examined the relations between obesity in parents and fat intake in their children, and the effect of fat intake on fat mass in these children. Our heterogenous sample (-x+/-SD: 20.2+/-3.4 kg; 3.2+/-1.3kg fat mass) consisted of 56 white and 15 Mohawk children 4-7 y of age (35 girls and 36 boys). Dietary intake was assessed with the Willett food-frequency questionnaire revised for children. Body composition was measured by bioelectrical resistance and subscapular and triceps skinfold thicknesses. Physical-activity energy expenditure was estimated by the difference between total energy expenditure (measured over 14 d by the doubly labeled water method) and postprandial resting energy expenditure (measured by indirect calorimetry). Before statistical analysis, fat mass was adjusted for fat-free mass, and fat intake was adjusted for nonfat intake. There was no effect of sex or ethnicity on fat intake and no effect of ethnicity on the relation between fat intake and fat mass. Adjusted mean (+/-SE) fat intakes for the groups of children, based on parental obesity status, were as follows: 1.65+/-0.09 MJ/d (nonobese mother and father), 2.58+/-0.10 MJ/d (obese father, nonobese mother), and 2.79+/-0.10 MJ/d (obese mother and father). We found an influence of maternal obesity on dietary fat intake in children (P=0.052) and a significant correlation between fat mass and fat intake in boys (r=0.48, P<0.01) but not in girls after adjustment for physical-activity energy expenditure. Our data suggest that 1)mothers may contribute to the development of obesity in children by influencing their dietary fat intake, and 2) dietary fat intake contributes to obesity in boys, independent of physical-activity energy expenditure.

Adipose Tissue↗