Platelets labeled with oxine complexes of Tc-99m and In-111. Part 2. Localization of experimentally induced vascular lesions.

Using rabbit platelets harvested and labeled with either Tc-99m or In-111 oxine as described in Part 1, we have successfully imaged experimentally induced fresh venous thrombi and newly injured arterial intima. Visualization of lesions up to 6 hr old is striking. Thrombi and arterial damage 24 hr old, however, were usually not imaged successfully; nor were preformed platelet-poor arterial emboli. The varying rates of platelet deposition in vascular lesions of different ages and types account for these observations. Should human cells prove as effective, widespread clinical application is anticipated.

Myocardial uptake of Tc-99m skeletal agents in the rat after experimental induction of microscopic foci of injury.

The cardiac uptake of Tc-99m tagged skeletal agents was studied after myocardial injury produced by subcutaneous catecholamine injection and random foot-shock stress. Rats stressed for 2 hr developed microfocal myocardial injury, without gross change, whereas those stressed for 12 hr sustained more confluent and sometimes grossly visible damage. Tc-99m MDP and Tc-99m PPi concentrations in these hearts were significantly above control (undamaged) heart levels, producing positive gamma-camera images. Subcutaneous epinephrine injections resulted in grossly visible lesions, with tracer concentrations higher than those previously reported in vasoocclusive infarcts. We postulate that the stress-induced scattered microfocal lesions may accumulate radiopharmaceutical on a per-gram basis in the same way as the larger catecholamine-induced lesions, since tracer delivery to the injured areas in each case is probably less impeded than in frankly vasoocclusive models. Such microfoci, then, could provide an explanation for some of the "false positive" myocardial scans observed clinically.

Preliminary report: Evaluation of tissue ingrowth into experimental Replamineform vascular prostheses.

A new experimental arterial prosthesis has been developed by replacing the minimal surface microporous calcite structure of sea urchine spines. Prostheses having a 4 mm. inside diameter and a homogenous 15 to 20 mu porous network have been prepared in bioelectric polyurethane and segmented polyurethane. Ten prostheses were placed in the femoral and carotid arteries of dogs weighing 27 to 35 kilograms and were harvested at a time interval of 3 to 14 days to characterize the tissue ingrowth. Eight of the ten prostheses were widely patent at time of harvest, with tissue ingrowth evident as early as the third day and with complete fibroblastic and capillary penetration of the 1 mm. thick walls developed by the end of one week. By 2 weeks there was uniform formation of 50 to 100 mu well organized neointimal surfaces.

The influence of chronic administration of hypnotics and analgesics on rate of recovery from inhalation anesthesia in rats.

A series of groups of Sprague-Dawley rats were given either secobarbital, phenobarbital, morphine, pentazocine, diazepam, methotrimeprazine, or saline (control) intraperitoneally on 4 consecutive days and then, on day 5, anesthetized with chloroform, trichlorethylene, fluroxene, halothane, methoxyflurane, enflurane, isoflurane, bromotrifluorocyclobutane, or chlorotrifluorocyclobutane. One control group received neither pretreatment nor anesthetics and another was given pretreatment but no anesthetics. The factor of "enzyme induction" is also evaluated, as are SGPT elevation and liver and kidney lesions. If enzyme induction occurred with the drugs used for pretreatment, the anesthetics suppressed the expected response. SGPT levels were generally within normal range. The combinations of all pretreatments with enflurane, halothane, or methoxyflurane had the fastest recovery; recovery was slower with the other anesthetic agents, but none of the prior chemotherapeutic drugs accelerated recovery from the inhalation anesthetics.