Effect of covalently bound heparin coating on patency and biocompatibility of long-term indwelling catheters in the rat jugular vein

Many physiologic and pharmacologic studies require long-term vascular access for repeated substance infusion and/or blood sample collection. The study reported here was undertaken to determine whether a functionally active heparin coating would improve long-term patency of venous catheters in rats. Uncoated or coated catheters were surgically placed in the jugular vein, and patency was evaluated twice weekly for a total of 30 days. Culturing of blood and catheters, and histologic examination were performed for all rats. All heparin-coated catheters remained patent for the study duration, with patency defined as ability to infuse saline and withdraw a blood sample. Median patency for uncoated catheters was 17.5 days, with a range of three to 30 days. Histologic evaluation of vessels revealed more advanced and severe lesions in rats with uncoated, compared with coated catheters. Furthermore, uncoated catheters had increased association with bacteremia (3/8), compared with coated (0/9) catheters. Taken together, these results indicate that coating catheters with covalently bound heparin molecules can significantly prolong patency and cause less pathologic damage to the catheterized vessel.

Oxymetholone: III. Evaluation in the p53+/- transgenic mouse model

Oxymetholone has been identified as a suspected nongenotoxic carcinogen and has recently completed testing in a conventional National Toxicology Program (NTP) 2-yr rodent bioassay program. As a synthetic androgen with a limited historical database in toxicology, oxymetholone is an ideal candidate for prospective examination of the performance of short-term transgenic mouse models in the detection of carcinogenic activity. In the present series of 3 articles, studies are described where oxymetholone was evaluated prior to disclosure of the results of the NTP 2-yr bioassay. The accompanying articles provide evidence showing that oxymetholone is devoid of mutagenic activity yet elicits a positive carcinogenic response in the Tg.AC transgenic mouse model. In the present study, oxymetholone was administered by oral gavage to p53 heterozygous male and female mice for 26 wk at doses of 125, 625, and 1,250 mg/kg/day. The vehicle was 0.5% aqueous methylcellulose. Positive controls consisted of mice treated daily by oral gavage with 200 or 400 mg/kg/day of p-cresidine in corn oil. The oxymetholone-treated females showed significantly increased body weight gain and clitoral enlargement attributable to drug treatment. In addition, significant alterations in kidney, liver, and testis weights were attributable to oxymetholone. However, there were no neoplastic lesions that were attributable to oxymetholone in either sex. p-Cresidine produced unequivocal bladder neoplasms in both sexes at the high dose and in males at the lower dose. The absence of a neoplastic response with oxymetholone is consistent with the selectivity of the p53-/- mouse model for detecting carcinogens that act by genotoxic mechanisms.

Acute toxicity, subchronic dermal toxicity, and delayed contact sensitization evaluations of dicyclopentenyloxyethyl methacrylate in rabbits and guinea pigs

The subchronic dermal toxicity of dicyclopentenyloxethyl methacrylate (DPOMA) was evaluated in young adult New Zealand White rabbits, and its potential to produce delayed contact sensitization was evaluated in Harley guinea pigs by a modified Buehler's closed patch technique. In addition, studies were conducted to evaluate the acute systemic toxicity of DPOMA in rats (oral) and rabbits (dermal), and its eye and skin irritancy in rabbits. In the subchronic dermal toxicity study, 4 groups of rabbits were treated percutaneously with DPOMA at 0 (acetone), 10, 107, and 1067 (undiluted) mg/kg X day in a volume of 1 ml/kg, over a 4-wk period. The application sites were unoccluded. No deaths occurred, and no signs of systemic toxicity were observed. No treatment-related effects were seen on body weights, hematology, clinical chemistry, urinalysis, organ weights, or histopathology (except the treated skin). The only treatment-related effect was slight to moderate skin irritation in the mid- and high-dose groups. The severity of skin irritaton was dependent on the number of applications and the concentration of DPOMA. Maximal skin irritation occurred after 1 wk. No skin irritation was seen in the control and low-dose group. In the DCS study, guinea pigs received 6 induction doses of 0.5 ml 100% DPOMA and were challenged with 0.5 ml of 50% (w/v) DPOMA in acetone 2 wk after the last induction treatment. No erythema or edema was observed in any of the challenged guinea pigs in either the treated and control groups. These acute toxicity studies indicate that DPOMA is practically nontoxic by a single exposure via both oral and dermal routes (the oral LD50 in rat and dermal LD50 in rabbits were greater than 5.0 g/kg body weight), slightly irritating to the skin, and inconsequentially irritating to the eyes. The no-observed-effect level (NOEL) for systemic toxicity of DPOMA applied repeatedly to rabbits skin is at least 1067 mg/kg X d. DPOMA is not a strong or moderate skin sensitizer in guinea pigs.

Acute myelomonocytic leukemia in a dog

An adult female Collie with anorexia, lethargy, posterior limb ataxia, and enterorrhagia had severe leukemia. In the peripheral blood were granulocytes, monocytes and cells with characteristics of both (myelomonocytic intermediates). The dog died within 17 days of the onset of illness. There were widely disseminated green-yellow foci of leukocytes of the same types as in the peripheral blood. A diagnosis of acute myelomonocytic leukemia was made.