PubMed Health⌕ Search

Biomedical subjects

D L Moyer

Publications and source records attributed to D L Moyer.

At least 37 records · Page 2Linked to original sources
PubMed1978

Effect of comonomer ratio on hydrocortisone diffusion from sustained-release composite capsules.

The daily in vitro release of hydrocortisone from composite polymer capsules is reported here for over 120 days. Increase in vinyl acetate comonomer content of the ethylene-vinyl acetate copolymer matrix brought about an increase in the diffusion rate. Variation in the initial drug content of the capsules from 40 mg to 20 mg affects the daily drug release less significantly than the variation in copolymer ratio. The correlation between vinyl acetate comonomer content and the percent crystallinity of the copolymer matrix is suggested as one of the possible major factors in controlling diffusion rate from this drug-polymer system. The diffusion constant (D) calculated was 0.212 X 10(10) cm2/sec when the copolymer carrier has 30% vinyl acetate content and 0.430 X 10(11) cm2/sec when the copolymer carrier has 20% vinyl acetate content for capsules with 20 mg initial drug content, and 0.118 X 10(-11) cm2/sec and 0.226 X 10(-11) cm2/sec, respectively, for capsules with 40 mg initial drug content.

Capsules↗
PubMed1978

Response of lymphoid leukemia L1210 in mice to implantable sustained release cytosine arabinoside capsules.

The lifespan of BDF mice with ascitic L1210 leukemia is more than doubled when they are treated with a single subcutaneously or intraperitoneally implanted sustained release cytosine arabinoside capsule. These capsules are drug-polymer composites, with dimensions of 1.0 cm in diameter and 0.15 cm in thickness, and a drug content of 17 +/- 3 mg each. Blank silicone rubber discs implanted intraperitoneally or subcutaneously in the leukemic mice produced no beneficial effects. Control healthy mice receiving the ARA-C releasing capsules continued to live with no obvious signs of drug toxicity. In vitro release of ARA-C from the discs was measured. Drug release was maintained above 20 micrograms per day for more than 35 days. ARA-C extracted from discs recovered from implant studies showed that less than 16% of the total drug content was released in vivo.

Animals↗
PubMed1978

Response of intramuscular Walker 256 rat tumor to sustained-release cyclophosphamide and ARA-C capsules.

Randomly bred Sprague-Dawley rats with the intramuscular form of Walker 256 tumor growing in the right thigh region were treated with sustained-release cyclophosphamide capsules as well as with cytosine arabinoside capsules. A disk-shaped caps-le was implanted subcutaneously adjacent to the tumor mass. Tumor regression, weight gain, and prolongation of lifespan were observed in animals treated with cyclophosphamide capsules of 10 mg or 20 mg total drug content each. However, the walker 256 intramuscular tumor did not respond to ARA-C capsules implanted, and the animals died at the same rate as the controls, with large ulcerated tumor masses and some metastasis. The in vitro diffusion data of ARA-C capsules is shown. Gross and histological changes associated with cyclophosphamide administered in this manner are reported.

Animals↗
PubMed1977

Effects of subcutaneously implanted sustained-release cyclophosphamide capsules on Walker 256 solid rat tumor.

Complete regression of Walker 256 solid rat tumor was brought about by the subcutaneous implantation of a single sustained-release cyclophosphamide capsule adjacent to the tumor mass. Untreated control animals died within 3 weeks after receiving the tumor with large necrotic masses. Rats with sustained-release capsules experienced complete tumor regression within 28 days. Upon examination, the tissues around the previous tumor mass has regenerated, and no viable tumor cells could be found in the area where the previous tumor mass was. Around the implanted sustained-release cyclophosphamide capsule a fibrous sheath has developed over the 3 weeks it was in situ. This study suggests an alternate means of cytoxic drug administration in the treatment of solid tumors in experimental animals.

Animals↗
PubMed1976

A unified mathematical model for diffusion from drug-polymer composite tablets.

The derivation and experimental verification of a unified mathematical model for the estimation of drug release rate from drug-polymer composite tablets are presented. Cylindrical coordinates are utilized in the solution of the diffusion equation for a three-dimensional system. The model is applicable to tablets that range from the shape of a flat disk (radius greater than thickness) to that of a cylindrical rod (radius less than thickness). The general solution for the fraction of drug released at a time t is (see article). This approach to a three-dimensional system, utilizing cylindrical coordinates, presents a comprehensive method for the estimation of drug release rates from sustained release tablets with drug distributed homogeneously throughout a polymer matrix. The calculated and experimental drug diffusion rate of pyrimethamine from pyrimethamine-silicone rubber composite tablets that range in shape from that of a disk to a cylinder, and of hydrocortisone from EVA, polycaprolactone, and PVA terpolymer, are compared.

Caprolactam↗
PubMed1976

Effects of intrauterine devices on nuclear deoxyribonucleic acid metabolism in rabbit blastocysts: an autoradiographic study.

A metabolic parameter, DNA synthesis, was measured in rabbit blastocysts exposed to Silastic intrauterine devices (IUDs) and compared with those without IUD exposure. Autoradiographic detection of 3H-thymidine uptake showed that the IUD-exposed blastocysts contained fewer labeled cells than their IUD-free equivalents. The depressed DNA synthesis may be caused by either a block in the cell cycle or a block in DNA synthesis itself. Either way, the result could be consistent with the observation that embryo deaths occur at all growth stages, preimplantation, during implantation, and postimplantation.

Animals↗
PubMed1975

3H2O volume and exchange in uterine cavity of monkeys.

A technique was developed to measure water exchange in the endometrical canal (uterine cavity). This type of determination should provide information necessary to understanding intrauterine pharmacokinetics. In the study described, measurements were performed on one cynomologus and four rhesus monkeys. Endometrial fluid in the uterine cavity was replaced with a 3H2O solution of known specific radioactivity (dpm/ml). Radioactivity remaining in the cavity at measured intervals of approximately 0.5, 1, 2, and 3 min following replacement was determined by flushing out the cavity. By extrapolating the 3H2O disappearance curve versus time to t = 0 (zero time), the apparent cavity volume (aVc) was derived. Values for aVc and t 1/2 3H2O were used to calculate endometrial fluid-water turnover rate. Mean values determined in four rhesus monkeys were as follows: aVc, 0.032 ml; t 1/2 H2O, 1.17 min; 24-h H2O turnover, 19.5 ml. In general, this value for H2O turnover was considerably higher than values of endometrial fluid production quantitated by other techniques. Water measurements in human uteri similar to those reported here appear feasible and are anticipated in future work.

Animals↗