In attempting to account for the ability of most solid tumors to restrict the absorption of WR-2721, aminopropyl-aminoethylphosphorothioate, we examined a number of drug characteristics which might allow for this restriction, and observed that drug hydrophilicity was a major contributing factor. When the highly hydrophilic WR-2721 was dephosphorylated, the drug became less hydrophilic and could readily cross tumor cell membranes. In addition, conventional radioprotectants, such as cysteine and mercaptoethylamine, were shown to be less hydrophilic than WR-2721 and also to cross tumor membranes readily. Therefore, drug hydrophilicity would appear to be the factor underlying the ability of WR-2721 to selectively protect normal tissues while most other protectors alter the radiation resistance of normal and tumor tissue alike. A red blood cell model for studying this problem in greater detail is described.

Absorption↗

PubMedDate not supplied

Morphologic evaluation of frozen rabbit and human ova.

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Animals↗

PubMedDate not supplied

Effects of structure of beta-cyclodextrin-containing polymers on gene delivery.

Linear cationic beta-cyclodextrin-based polymers (betaCDPs) are capable of forming polyplexes with nucleic acids and transfecting cultured cells. The betaCDPs are synthesized by the condensation of a diamino-cyclodextrin monomer A with a diimidate comonomer B. In this paper, the effects of polymer structure on polyplex formation, in vitro transfection efficiency and toxicity are elucidated. By comparison of the betaCDPs to polyamidines lacking cyclodextrins, the inclusion of a cyclodextrin moiety in the comonomer A units reduces the IC50s of the polymer by up to 3 orders of magnitude. The spacing between the cationic amidine groups is also important. Different polymers with 4, 5, 6, 7, 8, and 10 methylene units (betaCDP4, 5, 6, 7, 8, and 10) in the comonomer B molecule are synthesized. Transfection efficiency is dependent on comonomer B length with up to 20-fold difference between polymers. Optimum transfection is achieved with the betaCDP6 polymer. In vitro toxicity varied by 1 order of magnitude and the lowest toxicity is observed with betaCDP8. The LD40 of the betaCDP6 to mice is 200 mg/kg, making this polymer a promising agent for in vivo gene delivery applications.

Animals↗

PubMedDate not supplied

New class of polymers for the delivery of macromolecular therapeutics.

Cationic polymers show promise for the in vitro and in vivo delivery of macromolecular therapeutics. Known cationic polymers, e.g., poly(L)lysine (PLL) and polyethylenimine (PEI), have been employed in native and modified forms for the delivery of plasmid DNA (pDNA) and reveal varying levels of toxicity. Here, we report the preparation of a new class of cationic polymers that are specifically designed to deliver macromolecular therapeutics. Linear, cationic, beta-cyclodextrin (beta-CD)-containing polymers (CD-polymers) are synthesized by copolymerizing difunctionalized beta-CD monomers (AA) with other difunctionalized comonomers (BB) such that an AABBAABB product is formed. The beta-CD polymers are able to bind approximately 5 kbp pDNA above polymer to DNA (+/-) charge ratios of 1.5, compact the bound pDNA into particles of approximately 100-150 nm in size at charge ratios above 5+/-, and transfect cultured cells at charge ratios above 10+/-. In vitro transfections with the new beta-CD-polymers are comparable to the best results obtained in our hands with PEI and Lipofectamine. Some cell line-dependent toxicities are observed for serum-free transfections; however, no toxicity is revealed at charge ratios as high as 70+/- in transfections conducted in 10% serum. Single IV and IP doses as high as 200 mg/kg in mice showed no mortalities.

Animals↗

PubMedDate not supplied

Evaluation of cost-productivity of hospital-based general practice residency programs.

This study evaluated the 1985 cost-productivity of staff dentists and general practice residents at 11 dental clinics with general practice residency (GPR) programs and five nonteaching dental clinics in Veterans Administration hospitals. The results indicate that on the basis of dental service production, GPR facilities are or should be as cost-efficient as nonteaching facilities. It was also found that GP residents can repay a major part of their training costs.

Cost-Benefit Analysis↗

PubMedDate not supplied

Prevention of chlorphentermine-induced pulmonary phospholipidosis in rats by phenobarbital.

It has been shown previously that the induction of pulmonary phospholipidosis in rats by chlorphentermine (CP) is essentially prevented by the concurrent administration of phenobarbital (PB). This study was conducted to investigate the mechanism(s) responsible for this protection. Male Long-Evans hooded rats received either 14C-CP (30 mg/kg, ip) or both PB (30 mg/kg, po) and the 14C-CP daily for up to 1 week. Associated with the PB-induced prevention of phospholipid accumulation in the lungs was an 84% reduction in CP content in the tissue. Excretion in urine and feces was 55 and 6%, respectively, of the administered 14C for the CP group, and 66 and 11%, respectively, for the CP + PB group. Increased urinary excretion was not due to enhanced glomerular filtration or urine output. With each group, nearly 80% of the 14C was extracted into ether from alkalinized urine and co-chromatographed on TLC with pure CP. The difference in nonextractable 14C (presumably polar metabolites of CP) between the two groups is small and cannot account for the difference in total 14C excreted in the urine. All of the fecal 14C was CP. These experiments rule out an increase in CP metabolism as the primary basis for the CP-induced enhancement in 14C excretion. PB appears to actually protect against CP-induced pulmonary phospholipidosis rather than reversing it. This occurs by an enhancement in excretion of CP, thereby preventing it from reaching levels in the lungs which lead to PL accumulation.

Animals↗

PubMedDate not supplied

Absence of metabolism of morphine during accumulation by isolated perfused rabbit lung.

Pulmonary accumulation and metabolism of morphine was studied in an isolated perfused lung system. No metabolism of morphine or N-demethylation of ethylmorphine was found. Accumulation from the recirculating perfusate was nonsaturable over a concentration range of 3-400 microM morphine. Inhibition of sodium transport or sodium depletion decreased morphine accumulation. The results are most consistent with passive diffusion of morphine down an electrochemical gradient and subsequent nonspecific binding to tissue anions. Normal movement of sodium and potassium is required to maintain this gradient.

Animals↗