The biochemical and clinical consequences of 2'-deoxycoformycin in refractory lymphoproliferative malignancy

A deficiency of adenosine deaminase, an enzyme important in purine nucleoside catabolism, is associated with a severe combined immunodeficiency disease in children. Inhibition of this enzyme in vitro and in vivo results in an impairment in lymphoblast proliferation. We have investigated the pharmacologic inhibition of this enzyme by 2'-deoxycoformycin in 15 patients with hematologic malignancies. Biochemical consequences of the administration of this agent were closely monitored in erythrocytes, nucleated peripheral blood and bone marrow cells, serum, and urine. A marked rise in erythrocyte dATP was accompanied by a depletion of ATP in those patients exhibiting toxicity. Most patients excreted large amounts of deoxyadenosine but not adenosine in the urine. Serum deoxyadenosine rose in patients demonstrating a marked decrease in cell mass. The biochemical disturbances and clinical toxicity, including hepatic, renal, and conjunctival abnormalities, were usually reversible. Central nervous system toxicity, which potentially was the most serious consequence, was associated with high erythrocyte dATP/ATP ratios and high levels of cerebrospinal fluid deoxyadenosine. In patients with lymphoma and leukemia, objective responses were observed but were short- lived. Patients with chronic lymphocytic leukemia receiving weekly low doses of the drug demonstrated minimal toxicity and some efficacy. The chemotherapeutic potential o 2'-deoxycoformycin, as either a single agent or in combination with Ara-A, merits further exploration.     

TFT and 6TG resistance of mouse lymphoma cells to analogs of azacytidine

5-Azacytidine (5-aza-CR) and six of its analogs were examined for their ability to induce trifluorothymidine (TFT) and/or 6-thioguanine (6TG) resistance in L5178Y mouse lymphoma cells. These analogs were 5-aza-2'-deoxycytidine (5-aza-CdR), 5-fluoro-2'-deoxycytidine (5-FCdR), 5,6-dihydro-5-azacytidine (dH-aza-CR), 6-azacytidine (6-aza-CR), cytidine (CR) and 1-b-D-arabinofuranosylcytosine (ara-C). 5-Aza-CR and 6-aza-CR were examined for their ability to induce 6TG-resistant colonies and results demonstrated no effect. At least a 5-fold increase in TFT resistance was observed for 5-aza-CR, 5-aza-CdR, 5-FCdR, dH-aza-CR and ara-C. The concentration at which these compounds induced TFT resistance correlated well with the potential of the nucleoside analogs to induce differentiation in C3H10T1/2 cells as determined by Constantinides et al. (Nature, 267, 364-366, 1977). In L5178Y mouse lymphoma (MOLY) cells, 5-aza-CR induced TFT resistance and produced both small and large colonies. Previous studies using mammalian cells showed the absence of mutagenic activity with 5-aza-CR and some of its analogs at the ATPase and hgprt loci. However, the different spectrum of DNA lesions detected at the tk locus may be responsible for the response of MOLY cells to 5-aza-CR.     

Pharmacokinetics of nicotine and cotinine after application of two different nicotine patches under steady state conditions.

Tobacco use has resulted in major health related problems world-wide. Transdermal nicotine replacement therapy is one of the most promising strategies in smoking cessation. In the present trial the pharmacokinetic properties of two matrix patches (A and B) were characterized and compared after daily application on day 4. Predose nicotine concentrations on day 4 with patch B were higher than with patch A (12.7 +/- 9.5 ng/ml vs. 8.3 +/- 5.3 ng/ml). With patch A there was a steeper increase up to the peak level, followed by a decline gradually up to 24 h. 24 h after application predose levels were reached again, demonstrating absence of significant accumulation of nicotine. The calculated elimination half-lives of nicotine (3.4 +/- 1.8 h after patch A and 3.3 +/- 2.0 h after patch B) were longer than after i.v. application (published values range from 40 to 120 min). Under steady state cotinine concentrations remained constant.     

Prostaglandins and angioplasty. An experimental study in canine arteries

To prevent platelet aggregation following percutaneous transluminal angioplasty (PTA), cyclooxygenase inhibitors such as acetylsalicylic acid (ASA) and indomethacin are recommended. However, ASA blocks both the proaggregating effects of thromboxane (TXA2) and the antiaggregating and vasodilating effects of prostacyclin (PGI2). The authors measured the contractile response of dilated canine carotid arteries in situ and in vitro using an isometric force transducer. Following PTA, contraction of the arterial wall was significantly reduced (p less than 0.01). By blocking cyclooxygenase with indomethacin (3 micrograms/ml), contraction was greatly improved (p less than 0.001). These results suggest that PTA may result in marked release of prostacyclin by the damaged arterial wall, which could account for the decreased responsiveness of the artery to exogenous norepinephrine.     

Angiologic observations following autologous vein grafting and free radial artery flap elevation

Fifteen cases with radial forearm flap harvesting and autologous vein-graft reconstruction of the missing radial artery portion, are reported. Post-repair follow-up examinations, using segment plethysmography, photoplethysmography, and Doppler ultrasound, demonstrated an angiologic donor site morbidity, even when radial artery reconstruction was performed. Typically diminished blood pressure occurred, in comparison with the contralateral healthy extremity. Index shifting of pulse wave peaks, as well as widening of pulse wave bases occurred, especially in the thumb and index finger. These latter findings appear to be discrete indicators of arterial insufficiency.