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Biomedical subjects

M J Walters

Publications and source records attributed to M J Walters.

30 records · Page 2Linked to original sources
PubMed1983

Hormonal specificity and activation of sexual behavior in male zebra finches.

Castrated zebra finches receiving one of six hormone treatments were given three weekly tests with different females and their sexual behavior was contrasted with that of two control groups consisting of intact or castrated males given implants of cholesterol. The six hormone treatments were: two aromatizable androgens, testosterone (T) and androstenedione (AE); two nonaromatizable androgens, androsterone (AN) and dihydrotestosterone (DHT); an estrogen, estradiol (E); or a combination of E + DHT. Half the males receiving DHT received the 5 alpha-isomer, half received the 5 beta-isomer. Castration significantly reduced the proportion of males which courted females, total courtship displays, high-intensity courtship displays, beak wiping activity, and significantly increased the latencies to show these behaviors compared to intact males. Castrated males never attempted to mount a female. All of these measures of courtship and copulatory behavior were restored to normal levels only by treatments providing both estrogenic and alpha-androgenic metabolites (i.e., T, AE, E + alpha DHT). AE was clearly the most effective of these, raising behavior significantly above normal on several measures. AN treatment was more effective than alpha DHT on all measures and not significantly different from intact birds on some. Treatment with E, alpha DHT, beta DHT, or E + beta DHT was totally ineffective. Surprisingly, females only solicited males whose hormone treatments provided estrogenic metabolites. Not only did they solicit males given aromatizable androgens, which showed high rates of courtship activity, they also solicited males given E or E + beta DHT, some of which never even courted. Castration and hormone treatment also affected body and syringeal weight, but in opposite directions. Castration increased body weight while decreasing syringeal weight. Hormone treatments providing alpha-androgenic metabolites decreased body weight and increased syrinx weight. Treatments supplying estrogen as well were slightly more effective.

Androgens↗
PubMed1982

High-performance liquid chromatographic analysis of hydrocortisone drug substance, tablets, and enema.

Methods for the analysis of hydrocortisone drug substance, tablets, and enema were developed using adsorption high-performance liquid chromatography (HPLC). This HPLC system was shown to be capable of isolating hydrocortisone from its degradation products, synthesis precursor, and related corticosteroids. The accuracy, precision, and linearity of the HPLC assay methods and their applicability to commercial products has been demonstrated.

Chromatography, High Pressure Liquid↗
PubMed1982

Improved survival with aggressive surgical management of noncandidal fungal infections of the burn wound.

A period of aggressive surgical treatment of early identification of fungal infection of the burn wound was compared with the previous 5 years' experience with patients suffering from fungal infection of burn wounds. The portion of those patients with Candida infections diagnosed and treated premortem increased from 48.0% to 63.6% and of patients with noncandidal infections from 40.8% to 67.0% in the more recent period. The mortality of patients with Candida infections in 1973 to 1977 was 83.3% and in 1978 was 87.5%. The mortality of noncandidal infections, 87.4% in 1973 to 1977, was 25.0% in 1978. Local surgical control of the infected portion of burn wounds is an effective way of improving the survival in noncandidal burn wound infections. Surgical excision of burn wounds does not alter the poor prognosis of patients with Candida invasion of the burn wound.

Burns↗
PubMed1981

Changing trends in causalgia.

The term causalgia as currently understood encompasses a wider range of post-traumatic disabilities than Mitchell's original definition as burning pain. In this series, orthopedic injury replaced penetrating trauma as the most common initiating event. Injury to a peripheral nerve may be ill-defined or absent. Serious disability may arise from what appears to be a minor injury. When causalgia is recognized and appropriate therapy instituted, nearly all patients improve.

Causalgia↗
PubMed1978

High pressure liquid chromatographic determination of atropine sulfate and scopolamine hydrobromide in tablets.

A reverse phase high pressure liquid chromatographic (HPLC) system utilizing ion-pairing, similar to that previously reported for methscopolamine bromide, was developed for the quantitation of atropine sulfate and scopolamine hydrobromide in tablets. This HPLC system is capable of differentiating the major tropane alkaloids, with the exception of the atropine-hyoscyamine optical isomer pair, by their k' values and separating a significant degradation product, tropic acid. Optimum sensitivity is obtained by using a variable wavelength ultraviolet detector at 230 nm resulting in a detection limit of less than 0.5 microgram alkaloid/injection. The response is linear in the range of 3--19 microgram atropine sulfate and scopolamine hydrobromide. The coefficient of variation for injection reproducibility in less than 1%. The method has been applied to composite and individual tablet assays of scopolamine hydrobromide and atropine sulfate. The HPLC results are comparable (within 1%) to those obtained using the USP procedure; the HPLC method requires less sample preparation.

Atropine↗
PubMed1977

High-performance liquid chromatographic determination of diethylpropion hydrochloride in tablets: isolation and identification of two decomposition products.

A rapid assay was developed for diethylpropion hydrochloride tablets using high-performance liquid chromatography (HPLC) with UV detection. This technique provided separation of the drug from other UV-absorbing components present as the result of decomposition. A major decomposition product detected by HPLC in extracts of tablets and of the cotton filler from a tablet bottle was collected from the column effluents. This product was subsequently identified as 1-phenyl-1,2-propanedione, a highly volatile compound. A second decomposition product, isolated from decomposed drug by distillation from alkaline solution, was identified as diethylamine, apparently present as the hydrochloride salt, GLC, UV, IR, NMR, and mass spectrometry were used to confirm the identity of the decomposition products. HPLC assay results compared favorably with results of the NF assay; the latter procedure separated the drug from 1-phenyl-1,2-propanedione via liquid-liquid extraction.

Chromatography, Gas↗
PubMed1975

Consumer evaluation of health services: implications for methodology and health care policy.

Consumer evaluation research is defined and analyzed as an experimental model for establishing a link between social science research and public policy. The paper reports the results of an 18-month longitudinal study of an experimental citizen evaluation group. Participant observation was the method used to organize the data. The impact of the model on methodological issues, such as objectivity, researcher autonomy, and control over research decision-making are discussed. Implications of the consumer evaluation model for integrating social research and health policy formulation are analyzed and principles of citizen evaluation research are presented.

Consumer Behavior↗
PubMedDate not supplied

Analysis of illegally distributed anabolic steroid products by liquid chromatography with identity confirmation by mass spectrometry or infrared spectrophotometry.

Anabolic steroid products found in the illegal market are primarily oil-based injectables or tablets and often do not contain the ingredients declared on the label. An analytical scheme based on a reverse-phase liquid chromatographic (LC) system for screening, tentative identification, and quantitation is presented. Methanolic sample extracts are chromatographed on an octadecyl column using 2 mobile phases (methanol and (75 + 25) methanol-water) and tracked at 3 wavelengths (240, 210, and 280 nm) or with a photodiode array UV detector. Retention time ratios (RR) relative to testosterone and UV data are used for tentative identification. The same LC system serves as a cleanup and isolation step for identity confirmation by direct insertion probe mass spectrometry (MS) or Fourier transform infrared spectrophotometry (FTIR). Recoveries range from 96.2 to 100.2% for 11 different steroids extracted from sesame oil. LC RR values for over 40 steroids, analytical results for typical products, and MS and FTIR spectra for selected compounds are presented.

Anabolic Agents↗
PubMedDate not supplied

Classification of octadecyl-bonded liquid chromatography columns.

The differences in performance characteristics exhibited by columns available under the same octadecyl (C-18) label cause difficulties for the authors and users of official methods. This paper presents a simple scheme for classifying C-18 columns on the basis of the 2 predominant reverse phase retention mechanisms-hydrophobic and silanophilic interactions, which are dependent on the hydrocarbon coverage and the unreacted silanol sites, respectively. Hydrophobic interactions are represented by the ratio of anthracene k:benzene k in an acetonitrile-water (65 + 35) mobile phase. The unreacted silanols are represented by the N,N-diethyltoluamide k:anthracene k ratio with acetonitrile as the mobile phase. Column efficiency, which is largely dependent on particle size and packing technique, is included as a third classification criterion. Twelve brands of C-18 packings were subjected to this test scheme and qualitatively classified into 3 major groups on the basis of 3 criteria:hydrophobicity index, free silanol index, and efficiency. This scheme is intended as an aid in the selection of similar or equivalent columns and in defining the type of column suitable for an analytical method.

Chemical Phenomena↗
PubMedDate not supplied

Determination of histamine in fish by liquid chromatography with post-column reaction and fluorometric detection.

A liquid chromatographic (LC) system, using a bonded cation-exchange column, resolves histamine from histidine and other related compounds. Detection sensitivity and specificity are enhanced by introduction of a post-column reaction with o-phthalaldehyde to form a fluorescent derivative. The limit of detection is 1.5 ng histamine, and the response is linear over a range of 7-750 ng. The average histamine recovery from fortified tuna and mahimahi samples was 98.4% with a relative standard deviation of 2.18%. The results for canned tuna and mahimahi were comparable to those obtained by using the official AOAC method. The LC method requires only simple extraction of the sample before introduction into the LC system, which resolves and detects cadaverine and putrescine in addition to histamine.

Animals↗
PubMedDate not supplied

Liquid chromatographic determination of hydrocortisone in bulk drug substance and tablets: collaborative study.

A normal phase liquid chromatographic (LC) method for determining the hydrocortisone content of bulk drug substance, tablet composites, and individual tablets was subjected to a collaborative study by 6 laboratories. The results showed a mean recovery of 98.5% for an authentic tablet formulation and reproducibility coefficients of variation of 0.97, 1.6, and 2.7% for bulk drug substance, tablet composites, and individual tablets, respectively. Infrared (IR) and thin layer chromatographic (TLC) identification tests, also included in the collaborative study, were satisfactory. The LC method for determining hydrocortisone in bulk drug substance, tablet composites, and individual tablets, with IR and TLC identification, has been adopted official first action.

Chromatography, Liquid↗