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Biomedical subjects

R B Walker

Publications and source records attributed to R B Walker.

At least 37 records · Page 2Linked to original sources
PubMed1996

The effect on ephedrine prodrugs on locomotor activity in rats.

1. Five oxazolidines were synthesized by reaction of (-) ephedrine with formaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, and acetone, respectively. 2. Half-lives of hydrolysis were measured in pH 7.4 aqueous buffer. Half-lives varied from 12 seconds to 11 minutes. 3. The compounds were evaluated for their ability to increase locomotor activity in rats. All compounds significantly increased locomotor activity at 50 mg/kg dose. 4. The formaldehyde derivative had similar activity to (-) ephedrine. All other compounds were less active than (-) ephedrine.

Animals↗
PubMed1995

Sensitive high-performance liquid chromatographic determination of cyclizine and its demethylated metabolite, norcyclizine, in biological fluids using coulometric detection.

An accurate, sensitive, selective and reproducible high-performance liquid chromatographic method with coulometric detection for the determination of cyclizine and its inactive demethylated metabolite, norcyclizine, in biological fluids has been developed. The drugs were separated using a custom packed reversed-phase C18 analytical column and phosphate buffer (0.05 M, pH 3)-acetonitrile (7:3) as mobile phase. The dual electrode coulometric detector was operated in the "oxidative-screen" mode with the upstream electrode (detector 1) set at 0.55 V and the downstream electrode (detector 2) set at 0.90 V. Serum and urine samples were prepared for analysis by solid-phase extraction, followed by a simple phase-separation step. The limit of quantitation was 1 ng/ml for both cyclizine and norcyclizine in serum and urine.

Chromatography, High Pressure Liquid↗
PubMed1993

Nucleotide sequence of cDNA encoding the fire ant venom protein Sol i II.

For the first time the cDNA encoding a fire ant venom protein has been sequenced. Oligonucleotides were designed according to the amino acid sequence. The cDNA sequence was obtained by hybridizing these primers to mRNA and enhancement by the PCR technique. Comparison to the amino acid sequence of the venom protein shows a leader sequence 19 amino acids long.

Amino Acid Sequence↗
PubMed1993

Quantitative analyses of the coexistence of gamma-aminobutyric acid in substance P-amacrine cells of the larval tiger salamander retina.

The present study was performed as part of a systematic examination of gamma-aminobutyric acid's (GABA) coexistence with other classical transmitters and neuropeptides in neuronal populations of the larval tiger salamander retina. Substance P immunocytochemistry was combined with either GABA immunocytochemistry or autoradiography of high-affinity GABA uptake to examine for the presence of GABA in substance P-amacrine cells of the larval tiger salamander retina. Double-label analyses revealed two populations of substance P-amacrine cells that express both markers of GABA activity. One population was situated in the innermost cell row of the inner nuclear layer, while the other population was located in the ganglion cell layer. In both cases, these double-labelled cells accounted for approximately 10% of substance P-amacrine cells in their respective layers. The present study demonstrates, therefore, that substance P-amacrine cells in the larval tiger salamander retina can be categorized on the basis of their coexisting/non-coexisting relationships with GABA and suggests a possible functional diversity in the population of substance P-amacrine cells.

Ambystoma↗
PubMed1993

The effect of ephedrine isomers and their oxazolidines on locomotor activity in rats.

1. The four stereoisomeric ephedrines and four oxazolidines formed by reaction of each ephedrine isomer with salicylaldehyde were tested for their ability to increase locomotor activity in rats. 2. All ephedrine isomers except (-)pseudoephedrine increased locomotor activity; the order of potency was (-)ephedrine > (+) pseudoephedrine > (+) ephedrine. 3. All oxazolidine derivatives increased locomotor activity except (-)pseudoephedrine oxazolidine. 4. The oxazolidines derived from (-) and (+) ephedrine were slightly more active than their parent drugs. (+) Pseudoephedrine oxazolidine was less active than its parent. 5. Half-lives of hydrolysis were measured for the oxazolidines in aqueous buffer, ephedrine oxazolidines hydrolyze faster than pseudoephedrine oxazolidines.

Animals↗
PubMed1993

An epidemic of caterpillar sting dermatitis in a rural West Virginia community.

During a five-week interval which began May 1991, 19 patients presented to a community health center in a rural West Virginia community with a painful dermatitis. The dermatitis was caused by exposure to a single species of caterpillar, Hemileuca maia, larva of the buck moth. The caterpillars were apparently especially abundant during the period. Epidemics of caterpillar stings rarely have been reported. No previous epidemics of stings by the buck moth caterpillar have appeared in the literature.

Adolescent↗
PubMed1992

Effects of oxazolidines derived from (-) ephedrine in the rat.

1. Five oxazolidines were synthesized by reaction of (-) ephedrine with aliphatic aldehydes. The aldehydes used were formaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde and trimethylacetaldehye. 2. These five oxazolidines were tested in rats for ephedrine-like pharmacological activity using the hyperthermia and anorexia models. 3. All five oxazolidines caused significant elevation of body temperature in the hyperthermia model. The oxazolidine synthesized from (-) ephedrine and butyraldehyde caused greatest hyperthermia. 4. Four oxazolidines caused significant anorectic responses. The oxazolidine synthesized from (-) ephedrine and isobutyraldehyde caused greatest anorexia. 5. A possible tolerance to the anorectic effects of some of the compounds was observed.

Animals↗
PubMed1992

Exercise-induced bronchospasm in the young athlete: guidelines for routine screening and initial management.

Exercise induced bronchospasm (EIB) commonly occurs several minutes into or following an exercise event. Respiratory heat loss and respiratory water loss have been suspected as the precursor to exercise-induced bronchospasm. Obstructive EIB has been reported in elite Olympic athletes as well as the recreational athlete. Although exercise-induced bronchospasm presents as wheezing, chest tightness, or dizziness during or after exercise, cough post-exercise is a common and an easily detected characteristic of EIB. When exercise induced bronchospasm is suspected in the young athlete, an exercise challenge test should be performed. A 10% or more decrease in the peak expiratory flow rate in the post-exercise period is diagnostic of EIB. Once the diagnosis of EIB has been made, both nonpharmacological and pharmacological interventions are beneficial in reducing the airway responsiveness. Nonpharmacological measures include extensive education and cardiovascular fitness evaluation. Initial pharmacological management should consist of a trial of albuterol inhaler use 15 min prior to exercise. Early identification and treatment of EIB may enhance sports performance as well as enjoyment.

Adolescent↗
PubMed1991

Student athlete cholesterol screening during routine precompetition examination.

BACKGROUND: When properly organized and conducted, the preseason physical examination process for scholastic athletes can identify existing medical and musculoskeletal problems as well as provide for age-specific anticipatory guidance. This examination may also present an ideal opportunity to screen for adolescent hyperlipidemia. METHODS: Seven-hundred seventy-seven (777) students, aged 11 to 15 years, from seven junior high schools received fingerstick cholesterol screening during a complete preseason physical examination. Elevated values were verified by repeat examination. Values were compared with previously published national norms for this age group. All students received information on cholesterol, and the parents and pediatrician or family physician of those with confirmed positive tests (higher than 4.8 mmol/L [185 mg/dL]) were notified. RESULTS: One hundred fourteen (114), or approximately 15%, of the subjects were found to have elevated cholesterol levels. Of the 74 who returned for a second test, 38 (51%) were confirmed as having elevated cholesterol levels. Feedback from parents, principals, and coaches regarding the value of the screening and the associated education was overwhelmingly positive. CONCLUSIONS: In our experience, the precompetition examination provides an opportunity to screen for elevated cholesterol levels and to educate young people about hyperlipidemia.

Adolescent↗
PubMed1990

Hyperthermic and anorectic effects of oxazolidines derived from L-ephedrine in rats.

Oxazolidines synthesized from (-) ephedrine have been proposed as potential pro-drugs, but no pharmacological data on these compounds has been yet reported. In this study, four such compounds are tested in rats for ephedrine-like activity using the hyperthermia and anorexia models. The compounds were synthesized by reaction of (-) ephedrine with salicylaldehyde, acetone, cyclohexanone, and benzaldehyde, respectively. The results showed that all of the compounds decreased food intake significantly, but only the acetone and the salicylaldehyde derivatives caused a significant elevation of body temperature. All of the compounds were less effective than (-) ephedrine in the anorexia model. The acetone and salicylaldehyde derivatives showed similar potency to (-) ephedrine in the hyperthermia model.

Animals↗
PubMed1986

Exercise adaptation responses for gastric inhibitory polypeptide (GIP) and insulin in obese children. Possible extra-pancreatic effects.

Thirteen obese children and matched controls were fed a mixed meal, and responses were evaluated at fixed intervals for glucose, insulin, and gastric inhibitory polypeptide (GIP). The obese children were evaluated before and within 48 h after completion of a 5-mo exercise training program (ETP). The ETP included three aerobic exercise sessions per week and modest diet restrictions. Caloric expenditure was increased by approximately 300 kcal/exercise session. Weight gain was minimal over the 5 mo. An unexpected increase in GIP response and improved insulin tolerance were recorded for the obese children post-ETP. GIP values were higher (P less than 0.05) at 30 and 60 min and led to a highly significant elevation (P less than 0.01) of the integrated GIP response for post-ETP obese versus both pre-ETP and normal-weight controls. Insulin values were lower (P less than 0.05) at 30 and 60 min and led to a lower integrated insulin response (P less than 0.0585) for post-ETP obese children. However, the obese children continued to secrete more insulin (P less than 0.05) than normal-weight controls. Glucose tolerance, similar for pre-ETP obese subjects and controls, did not change in post-ETP children. Exercise-induced improvement in glucose utilization in these obese children was associated with an increase in GIP secretion. This contrasts with reports that calorie restriction will improve glucose utilization with decreased insulin and GIP secretion. The study demonstrates a previously unreported uncoupling of GIP and insulin secretion and suggests shifts in peripheral tissue sensitivity to insulin-induced glucose uptake. These shifts may, in part, be influenced by GIP.

Adolescent↗
PubMed1982

Moderate diet control in children: the effects on metabolic indicators that predict obesity-related degenerative diseases.

Nine prepubertal obese boys ages 9 1/2 to 12 yr followed moderately restricted diets and moderate exercise routine for 31 wk. Foods were selected from the family's basic diet and the physical activities were tailored to the home environment. This dietary (approximate decrease of 600 kcal/day) and activity (approximate increase of 300 kcal/day) intervention program was sufficient to stop weight gain and normalize key metabolic indices for prediction of atherosclerosis, hypertension, and diabetes. Throughout the treatment period serum lipid responses included significantly lower (p less than 0.05) total cholesterol, low-density lipoprotein-cholesterol and triglycerides. High-density lipoprotein-cholesterol was constant throughout the period. Responses in carbohydrate metabolism included significantly lower (p less than 0.05) fasting insulin and glucose. Insulin and glucose levels were positively correlated with total caloric consumption and insulin was also positively correlated with sucrose consumption (p less than 0.05). Fasting insulin/glucose ratios and glycosylated Hb decreased throughout the treatment period, but serum glucagon levels remained constant. In response to a glucose load, insulin and glucose decreased significantly by wk 31 of treatment. A practical approach for normalizing metabolism in obese male children is presented.

Arteriosclerosis↗
PubMed1982

Childhood accidents in a rural community: a five-year study.

Childhood accidents were monitored over a five-year period in a rural West Virginia primary care center. A population of 1,410 families with children up to 12 years of age was followed. Lacerations, musculoskeletal injuries, and head injuries were the most common injuries. Accidents were relatively more frequent within families with lower income levels and in single-parent households. The data suggest specific preventive strategies for this rural population.

Accident Prevention↗