Transition across polymorphic phenotypes observed in a male Sternarchogiton nattereri (Gymnotiformes: Apteronotidae).

A transition between polymorphic phenotypes was observed within a single male Sternarchogiton nattereri. This individual was initially toothless, but developed into a toothed phenotype characterized by a swollen distal upper jaw and distinctive external dentition. Changes in morphological features were accompanied by shifts in electrocommunication (chirping) behaviour.

Coronary reperfusion in primates. Serial electrocardiographic and histologic assessment.

After acute coronary occlusion in primates, the time period during which reperfusion results in significant salvage of reversibly injured myocardium was investigated. In 23 monkeys, the left anterior descending coronary artery was occluded from 1 to 6 h; and in 5 others, occlusion was maintained for the 1-wk study. Unipolar epicardial electrocardiograms were monitored from mapping points on the anterior and lateral left venticle. S-T segment elevation (S-T upward arrow) and R + S wave amplitude (RS) were measured before occlusion and at regular intervals during occlusion and reperfusion. Summated S-T upward arrow (SigmaS-T upward arrow) and summated RS (SigmaRS), computed for mapping points demonstrating greater than 2 mV S-T upward arrow, were used as serial measures of electrical injury. SigmaS-T upward arrow peaked within 2-h postocclusion and then gradually declined throughout the period of occlusion suggesting the progress of infarction within the area of injury. After reperfusion SigmaS-T upward arrow rapidly declined to near cnotrol values indicating the extent of reversible injury. During the period of occlusion, the magnitude of voltage loss in SigmaS-T upward arrow as a percent of maximum SigmaS-T upward arrow was proportional to the duration of occlusion, though the rate of loss decreased with increasing time of occlusion. Reperfusion after 6 h of occlusion resulted in reversal of only a small remaining component of the maximum current of injury. The voltage decrease in SigmaRS (from control values) was proportional to the duration of occlusion, though the decrease was accelerated during the first 2-h postocclusion. Whereas reperfusion interrupted the decline in SigmaRS, a consistent increase in SigmaRS postreperfusion was observed only after occlusion of 1 h. With respect to reperfusion groups, significance in SigmaS-T upward arrow voltage loss as a percent of maximum SigmaS-T upward arrow was demonstrated between 2-h and 4-h, 4- and 6-h, and 6-h and chronically ligated animals. Significance in SigmaRS voltage loss as a percent of control SigmaRS was demonstrated between 2- and 4-h, and 4- and 6-h reperfusion groups. Hearts were excised at 7 days for histological assessment of infarct size. Planimetric determination of left ventricular areas and areas of necrosis using slides made from 10 serial cross sections were used in estimating the percent of left ventricle infarcted. A significant reduction in infarct size was demonstrated between reperfused animals at 2 h and the 4- and 6-h reperfusion groups. A trend was noted suggesting increasing infarct size up to 6 h after experimental occlusion.

Specific potentiation of L1210 vaccine by pyran copolymer.

Pyran copolymer (NSC 46015) was found to potentiate strongly the immune response of C57BL/6J X DBA/2 F1 mice to 10(4) live L1210 tumor cells following suboptimal vaccination with 10(7) radiation-inactivated L1210 cells. Optimal immunity to challenge was produced by concomitant i.p administration of pyran and L1210 vaccine, and activity was dependent upon both pyran and vaccine dosages. In addition, this immunopotentiation seemed to be related to the intrinsic viscosity of different pyran preparations tested, although all the pyran compounds had significant activity. Furthermore, the increased immunity of subsequent live tumor challenge appeared to be specific for the vaccinating cell type.

Quantitative effect of a single large dose of methylprednisolone on infarct size in baboons.

Despite numerous studies directed at determining the ability of glucocorticoids to minimise myocardial ischaemic damage following acute coronary occlusion, there remains no clear consensus concerning their usefulness. Within an ischaemic region, glucocorticoids produce membrane stabilising effects which decrease the autolytic effects of marked cellular swelling and lysosomal membrane rupture. Their use has also been associated with a decreased cellular lysis due to infiltrating inflammatory cells and with an increase in collateral blood flow. The use of glucocorticoids has remained clinically attractive due to experimental observations regarding these local actions; however, the potential of these actions to enhance long-term viability of ischaemic myocardium has remained uncertain. A major problem in the comparison of the extent of infarction between treated and untreated animals has been the variability in infarct size that results from coronary artery ligation at any given anatomical site. In the experimental baboon model which we have employed, we have previously shown that the ultimate epicardial area of infarction, as well as the volume of infarction as assessed histologically at 7 days post occlusion, shows a good linear relationship to the area of ischaemic injury at 1-hour post occlusion, as assessed by high resolution epicardial ST segment mapping. In this way animals may serve as their own controls and as long as an intervention is initiated at 1 h or later post occlusion, then the epicardial area or transmural volume of histologically assessed infarction at 7 days can be compared with the predicted epicardial area or transmural volume of infarction and hence determine the effect of that intervention in altering infarct size. This experimental model does not rely on a comparison of the absolute magnitude of infarcts between treated and untreated animals and, therefore, avoids the error introduced by the inherent variability in infarct size between animals after coronary occlusion.

Error analysis of the double-integral method for calculating brain blood perfusion from inert gas clearance data.

A single-photon dynamic computer-assisted tomograph (DSPECT) has been built and is currently being used to evaluate regional cerebral blood perfusion in patients and volunteers. A computer simulation of the system was created to analyze the effects of data collection, Poisson noise, attenuation compensation, and the reconstruction technique now employed in the DSPECT. Several methods of attenuation compensation were used to generate perfusion images from both ideal and noisy data. The results indicate that the mean perfusion is calculated to within 10.4% accuracy for all perfusion rates in a region of interest if attenuation correction is used. Without attenuation correction, perfusions are underestimated by as much as 27%. The three correctors tested have different effects on the calculated perfusion value, depending on the location of the region of interest in the picture. The algorithm introduces random noise that is proportional to both the random error in the input data and the perfusion rate. Air-curve delay errors result in inaccuracies in the final perfusion picture that are proportional to perfusion rate. Physiological values (0.8-1.5) of the partition coefficient cause overestimation of both gray (0-34%) and white (7-67%) matter perfusion values. Compton scatter and collimator effects were not addressed in this study.

Parvocells: a novel interneuron type in the pacemaker nucleus of a weakly electric fish.

Gymnotiform weakly electric fish produce electric organ discharges (EODs) that function in electrolocation and communication. The command signal for the EOD is produced by the medullary pacemaker nucleus, which contains two well-characterized neuron types: pacemaker cells and relay cells. In this study, we characterized a third neuron type in the pacemaker nucleus. These neurons, which we have named parvocells, were smaller (7-15 microm in diameter) than relay and pacemaker cells. The parvocells were labeled with an antibody against the neuronal calcium-binding protein, parvalbumin, and were not labeled with several glial-specific antibodies. Parvocells had one to three fine processes that often terminated at the periphery of relay and pacemaker cell bodies. The parvalbumin-positive terminals of the parvocells colocalized with immunoreactivity for SV-2, suggesting that the parvocells form chemical synapses on the relay and pacemaker cells. Parvalbumin-positive neurons are frequently gamma-aminobutyric acid (GABA)ergic or glycinergic, and the cytoplasm of the parvocell somata was immunoreactive with a glycine antibody. Antibodies against glycine receptors and gephyrin, however, did not label any cells in the pacemaker nucleus, suggesting that the pacemaker nucleus does not contain glycine or GABA((A)) receptors. Electron microscopy revealed gap junctions between the membranes of parvocells and adjacent terminal-like structures. Furthermore, neurobiotin injected into individual pacemaker or relay cells labeled parvocells as well as other pacemaker and relay cells, demonstrating that the parvocells are dye-coupled to the other neuron types in the pacemaker nucleus. These findings indicate that the parvocells are histochemically distinct from relay and pacemaker cells and that they receive electrotonic inputs from and make chemical synapses back onto pacemaker and relay cells. Further study is needed to investigate the function of these neurons in regulating the EOD.

Seasonal changes in the size of the avian song control nucleus HVC defined by multiple histological markers.

Bird song is controlled by a discrete network of brain nuclei. The size of several song control nuclei changes seasonally in many seasonally breeding songbird species. Reports of seasonal changes in the size of song nuclei have relied primarily on Nissl stains to define the borders of these regions. Recent studies found that the size of the song nucleus higher vocal center (HVC) in male canaries did not change seasonally when its borders were defined by histological markers other than Nissl staining. We used three labels to define the borders of the HVC in male Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii): Nissl staining, the distribution of acetylcholinesterase-positive neuropil, and the distribution of neurons projecting to another song nucleus, area X. The HVC was larger in males exposed to a breeding photoperiod and testosterone concentrations than in males exposed to a nonbreeding photoperiod and testosterone concentrations, regardless of which of these three methods was used to define the borders of the HVC. This result suggests that seasonal changes in the Nissl-defined borders of the HVC reflect changes in the distribution of physiologically relevant markers of the nucleus and are not merely artifacts of the Nissl-staining method.

Seasonal plasticity and sexual dimorphism in the avian song control system: stereological measurement of neuron density and number.

Differences in neuron density and number are associated with seasonal plasticity and sexual dimorphism in the avian song control system. In previous studies, neuron density and number in this system have been quantified primarily through nonstereological approaches in thick tissue sections by using the nucleolus as the unit of count. The reported differences between seasons and sexes may be inaccurate due to biases introduced by neuron splitting during sectioning. We used the unbiased optical disector technique on tissue from three previous studies (two investigations of seasonal plasticity and one investigation of sexual dimorphism in avian song nuclei) to assess seasonal and sex differences in neuron density and number. In two song nuclei, HVc and the robust nucleus of the archistriatum (RA), the optical disector yielded intergroup differences in neuron density and number that coincided well with the three previous reports. We also estimated neuron number and density with a random, systematic, nonstereological counting protocol that used the neuronal nucleolus as the unit of count. We compared this method directly to the optical disector. In all cases, the two neuron-counting methods produced similar estimates of neuron number and density; the differences between treatment groups were equally discernible regardless of the counting method used. This study confirms previously reported seasonal and sex differences in the HVc and the RA by use of stereology and indicates that a random, systematic, nonstereological neuron-counting protocol is accurate and is well suited to the study of these phenomena in the avian song control system.

Alcoholism and memory: broadening the scope of alcohol-expectancy research.

Current biopsychosocial research on the etiology of alcoholism has begun to focus on memory processes as a possible common pathway for drinking decisions. The alcohol-expectancy construct is rooted both in cognitive psychology and alcohol research and can serve as a vehicle for this study. Reexamination of one recent review of issues in alcohol-expectancy research provides an opportunity to broaden the scope of this research with theoretical and methodological alternatives to those suggested in that review. Most importantly, this article shows that expectancy findings, discussed by Leigh (1989a) as reflecting "psychometric" limitations, are instead quite consistent with recent network models of memory structure. Such models can provide an informative guide to future research activities. It is also recommended that alcohol-expectancy research remain open to inputs from expectancy theories already developed in several psychological domains, as well as to theories of social cognition and attitude structure in addition to those advanced by Leigh.

Use of PG-21 immunocytochemistry to detect androgen receptors in the songbird brain.

The avian song control system is an excellent model in which to study the effects of gonadal steroid hormones on neural and behavioral plasticity. Several of the brain regions that control song behavior concentrate androgens and/or estrogens. Investigations of the distribution and regulation of androgen receptors have been limited by the lack of a reliable immunocytochemical method to detect androgen receptors in the songbird brain. We describe a protocol by which the PG-21 polygonal antibody to the rat androgen receptor can be used to label androgen receptor-containing cells in the songbird brain. By treating songbirds of several species with testosterone 90 min before sacrifice and by using relatively low concentrations (0.5 0.75 microg/ml) of PG-21 antibody to reduce nonspecific background staining, we were able to obtain strong specific labeling of cell nuclei in androgen-sensitive brain regions. This technique will facilitate the study of the role of androgens in mediating neural plasticity in the avian brain. Testosterone pretreatment may also facilitate the use of this antibody to label androgen receptors in tissues from a wide array of nonmammalian species.

The diagnostic utility of the lognormal behavior of PET standardized uptake values in tumors.

UNLABELLED: A meta-analysis of data primarily from PET oncologic investigations using FDG PET was performed. Its purpose was to establish statistical features of the distributions of standardized uptake values (SUVs) as possible aids in the diagnostic process. METHODS: We obtained 1536 values of oncologic markers from patient studies of 40 investigations in the literature. Statistical parameters were tabulated for analysis. RESULTS: A significant observation is that, unlike skewed SUV histograms, log10SUV has Gaussian behavior, which is not uncommon for biologic quantities. This was found for SUVs of FDG and 2 amino acids as well as a few other cancer markers. A possible model for explaining this is proposed. For FDG, the SD sigma of the log10SUVs for an average cancer category was 0.23. Examining data within the framework of the model points to physiologic factors as dominating SUV variability rather than PET protocols. When data for a single cancer category were available from multiple institutions, averages, mean(SUV)s, disagree beyond chance expectations. Diagnostic utility suggestions include a universal linear relationship between sensitivity and severity, defined as SUV/mean(SUV), on semilogarithmic probability paper; a generic receiver-operating-characteristic curve for all cancers; using [log10(mean(SUVmal)/mean(SUVnorm))] divided by (sigma(mal)2 + sigma(norm)2)(1/2) as a simple diagnostic effectiveness measure; and using Gaussian log10SUVs to avoid erroneous P values. CONCLUSION: Using the logarithms of markers, such as SUVs, several advantages stemming from their Gaussian nature can be achieved with benefits ensuing to the diagnostic process.

Hepatic extraction efficiency and excretion rate of technetium-99m-mebrofenin in dogs.

UNLABELLED: Quantitative hepatobiliary scintigraphy aids in the diagnosis of hepatic disease. Two scintigraphic parameters that have great value in discriminating between hepatocellular and biliary disease are hepatic extraction fraction (HEF), which is a measure of the hepatic extraction efficiency (HEE), and hepatic excretion rate. It is generally accepted that hepatic extraction fraction is normally 100%, but a review of the literature provided little information on the actual HEF of 99mTc-mebrofenin. METHODS: We determined the HEE of 99mTc-mebrofenin in nine normal dogs after direct injection into the afferent hepatic vasculature using a two-compartment model. The forward and reverse rate constants for the two-compartment model were solved by a simple graphic approach and a more complex numerical approach using a nonlinear least squares algorthm. The HEEs were determined using both methods. RESULTS: The HEE for the graphic and numerical methods of analysis were not significantly different and were calculated to be 92.2 +/- 4.75% (mean +/- s.d.) and 91.2 +/- 4.44% (mean +/- s.d.) by each method, respectively. The half-time clearance of 99mTc-mebrofenin was 19.10 +/- 4.86 min (mean +/- s.d.). CONCLUSION: This study validates the assumption that the normal HEE of 99mTc-mebrofenin is nearly 100%, barring species differences.

Hepatic extraction efficiency of technetium-99m-mebrofenin in the dog with toxic-induced acute liver disease.

UNLABELLED: Extraction of the hepatobiliary radiopharmaceutical 99mTc-N-(3-bromo-2,4,6-trimethyacetanilide) iminodiacetic acid (mebrofenin; Choletec, Squibb Diagnostic, Princeton, NJ) by the liver may be used as an index of hepatocellular function. The hepatic parenchymal cells extract mebrofenin from the blood using the same active transport mechanism as bilirubin. METHODS: In this study, we induced hepatocellular disease by administering a hepatotoxic drug and compared the hepatic extraction efficiency (HEE), measured directly from an afferent injection of 99mTc-mebrofenin, to quantitative histopathology and to serum biochemistry analysis. RESULTS: The baseline HEE was 95.9% +/- 2.71% (mean +/- s.d.). Dogs that were affected by the hepatotoxic drug had reduced HEE. HEE correlated well to the severity of histologic lesions (r = -0.83, p = 0.003). HEE also correlated well to the increases in the activities of alanine aminotransferase (ALT; r = -0.85, p = 0.002) and aspartate aminotransferase (AST; r = -0.89, p = <0.001), the concentration of fasting bile acid (r = -0.97, p = <0.001), bilirubin (r = -0.92, p = <0.001) and, to a lesser degree, to the activities of alkaline phosphatase (Alk Phos; r = -0.73, p = 0.016). HEE had higher correlation coefficients to the serum biochemistry analysis than did the quantitative liver histopathology. CONCLUSION: Hepatic extraction of 99mTc-mebrofenin is a good predictor of the severity of hepatocellular damage in toxic-induced liver disease.

Assessment of skeletal muscle viability by PET.

UNLABELLED: We investigated the use of [18F]fluoro-2-deoxyglucose (FDG) PET scanning for assessment of skeletal muscle viability in patients with peripheral vascular disease and in patients following free-flap skeletal muscle transfer for closure of open wounds. METHODS: We obtained 32 FDG-PET scans from 30 patients, either at the time of admission for peripheral vascular disease (n = 16) or between 1 and 15 days after surgery for skeletal muscle transfer (n = 16). Ratios between injured and contralateral limb FDG tracer activity uptake were correlated with clinical outcome at 1 mo to 3 yr follow-up. RESULTS: Viable muscle uptake ratios ranged from 0.47 to 7.88 (mean: 2.26 +/- 1.81; n = 26), while nonviable muscle uptake ratios ranged from 0.12 to 0.46 (mean: 0.27 +/- 0.12; n = 6; p < 0.02). After skeletal muscle transfer, two patients with viable tissue, as documented by PET, required amputation due to osteomyelitis, and one patient with peripheral vascular disease who showed viable tissue by PET required amputation 3 mo after the PET scan because of recurrent ulcers. CONCLUSION: FDG-PET scanning can determine skeletal muscle viability in patients with peripheral vascular disease and in patients following free-flap transfer.

Evaluation of fluorine-18-BPA-fructose for boron neutron capture treatment planning.

UNLABELLED: Boron neutron capture therapy (BNCT) using 4-[10B]boronophenylalanine-fructose (BPA-Fr) is in Phase II clinical trials to validate BNCT as a treatment for glioblastoma multiforme and melanoma. Successful BNCT depends on knowledge of the distribution of boron-containing agents in both tumor and normal tissue as currently determined by chemical confirmation of boron deposition in surgically removed malignant tissue before BNCT. METHODS: We used PET to noninvasively obtain in vivo information on the pharmacokinetics of the 18F-labeled analog of BPA-Fr in two patients with glioblastoma multiforme. Time-activity curves generated from the bolus injection of 18F-BPA-Fr were coinvolved to simulate a continuous infusion used for BNCT therapy. RESULTS: Distribution of 18F-BPA-Fr by PET was found to be consistent with tumor as identified by MR imaging. The 18F-BPA-Fr tumor-to-normal brain uptake ratio was 1.9 in Patient 1 and 3.1 in Patient 2 at 52 min after injection. The 18F-BPA-Fr uptake ratio in glioblastoma paralleled that of nonlabeled BPA-Fr seen in patients as previously determined by boron analysis of human glioblastoma tissue obtained from pre-BNCT surgical biopsy. CONCLUSION: Knowledge of the biodistribution of BPA-Fr enables pre-BNCT calculation of expected tissue dosimetry for a selected dose of BPA-Fr at a specific neutron exposure. Fluorine-18-BPA-Fr PET is capable of providing in vivo BPA-Fr biodistribution data that may prove valuable for patient selection and pre-BNCT treatment planning.

Reduction in infarct size by synchronized selective coronary venous retroperfusion of arterialized blood.

The effectiveness of selective synchronized pulsatile coronary venous retroperfusion for the temporary metabolic support of a region of acutely ischemic myocardium has previously been demonstrated. This study was designed to determine the degree of reduction in ultimate infarct size that may be achieved when coronary venous retroperfusion initiated early after coronary occlusion is combined with later anterograde reperfusion. In 10 baboons, the proximal left anterior descending coronary artery was occluded for 4 hours at which time anterograde reperfusion was restored. In five baboons (Group A), coronary venous retroperfusion was initiated 15 minutes after occlusion. Five baboons (Group B) underwent an identical procedure without coronary venous retroperfusion. Epicardial electrograms were recorded from 24 sites overlying the ischemic region. At 24 hours, hearts were excised and serial transverse sections of the left ventricle were stained with nitroblue tetrazolium for stereometric determination of infarct size. In Group A 12 +/- 5.4 percent (mean +/- standard error of the mean) of epicardial sites with S-T segment elevation at 15 minutes after occlusion showed subsequent Q waves, compared with 96 +/- 2.3 percent in Group B (p less than 0.01). In Group A 4.8 +/- 1.7 percent of the left ventricular mass was infarcted, compared with 30.6 +/- 4.2 percent in Group B (p less than 0.01). The results demonstrated the effectiveness of coronary venous retroperfusion in preserving ischemic myocardium such that anterograde reperfusion resulted in a mean reduction of 84 percent in ultimate infarct size.

Failure of nifedipine therapy to reduce myocardial infarct size in the baboon.

The value of nifedipine in reducing the ultimate size of an infarct associated with a period of coronary occlusion followed by reperfusion was assessed. Eight baboons were administered a bolus dose of nifedipine, 5 micrograms/kg intravenously, and then a maintenance dose of 30 micrograms/kg per hour was begun 1 hour before occlusion. This regimen resulted in an 8.5 +/- 1.2 percent (mean +/- standard error) decrease in mean arterial pressure. The left anterior descending coronary artery was occluded for 2 hours and then perfusion restored. At 2 hours after reperfusion the nifedipine infusion was discontinued. Eight control baboons underwent an identical protocol without nifedipine therapy. At 24 hours after occlusion, microvascular dyes were injected into the left anterior descending coronary artery and adjacent arteries to delineate the perfusion bed of the previously occluded artery. The volume of infarction was determined with planimetry and compared with the volume of the perfusion bed of the occluded artery. The area of infarction was always contained within the perfusion bed of the occluded artery. The mean percent of the perfusion bed with infarction was 50.1 +/- 5.8 in the control group and 41.7 +/- 9.5 in the treated group (difference not significant; p greater than 0.05). In both control and treated groups of baboons hemorrhage occurred only within the region of infarction. In both groups electron microscopy revealed large electron-dense granules within the mitochondria. In conclusion nifedipine therapy during a 2 hour period of coronary occlusion followed by reperfusion did not result in any significant reduction in ultimate infarct size in the baboon.

Quantitative assessment in infarct size reduction by coronary venous retroperfusion in baboons.

Initial favorable reports in which coronary venous retroperfusion was begun after acute coronary artery occlusion have demonstrated a reversal of ischemic injury and improved left ventricular function. However, little information has been generated to document the extent to which retroperfusion may decrease ultimate histologically determined infarct size. The objective of the present study was to evaluate the effectiveness of retroperfusion in reducing infarct size by using an accurate quantitative method in which infarct size was related to the size of the anatomic perfusion bed of the occluded artery (region at risk for infarction). In an experimental group of 5 baboons, the left anterior descending coronary artery was occluded and coronary venous retroperfusion started 1 hour after occlusion. After a 4-hour period of occlusion, retroperfusion was discontinued and anterograde perfusion was simultaneously restored. A control group of 5 baboons underwent an identical procedure without retroperfusion. Twenty-four hours after occlusion, hearts were excised and the previously occluded left anterior descending coronary artery as well as the adjacent arteries were infected with microvascular dye to delineate the perfusion bed of the occluded artery. Planimetry of serial corss-sections of the left ventricle enabled the size of the perfusion bed of the occluded artery and size of the infarct to be determined. The mean percentage of the perfusion bed infarcted in the control group was 94.1 +/- 0.9 (mean +/- standard error) and in the retroperfused group was 57.4 +/- 3.5 (p less than 0.001). Hence, the results demonstrated that when retroperfusion was initiated after 1 hour of coronary occlusion, the mean percentage of the perfusion bed salvaged was increased by 36.7%.

Inactivity of fecapentaene-12 as a rodent carcinogen or tumor initiator.

The possible carcinogenic activity of synthetic fecapentaene-12 (FP-12) was studied in several mammalian test systems: (a) for carcinogenicity by intrarectal instillation in male F344/NCr rats as well as by intrarectal and subcutaneous application in male B6C3F1 mice; (b) for initiation by skin painting in female SENCAR mice followed by repeated applications of 12-O-tetradecanoylphorbol-13-acetate (TPA), with 7,12-dimethylbenz[a]anthracene (DMBA) followed by TPA as positive control; (c) in a rat subcutaneous granuloma pouch assay in which mutagenicity was measured by induction of 6-thioguanine (6-TG) resistance and carcinogenicity was determined by induction of subcutaneous tumors in the pouch. There was no significant increase in tumor incidence after 72-78 weeks in test (a), although 2 rats receiving FP-12 intrarectally developed colon polyps. FP-12 did not initiate any skin tumors in test (b), nor did it significantly convert DMBA-initiated papillomas into carcinomas when 8 of the positive control mice were given FP-12 weekly for 10 weeks after 10 weeks on the DMBA-TPA regimen. Although FP-12 and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were comparably mutagenic in test (c), FP-12 induced no tumors after more than a year in 133 rats at risk while MNNG induced 7 tumors in 107 rats. These rodent assays provide no evidence that FP-12 is a strong carcinogen, although the possibility remains that it may possess weak carcinogenic activity not revealed by these experiments.

Hemorrhagic infarction and coronary reperfusion.

Coronary ligation experiments were performed on 23 primates. Some of the experiments were followed by reperfusion after periods of occlusion of from 1 to 6 hours. Hemorrhage into the infarct was noted in all animals and was greatest following reperfusion after 4 hours of occlusion or longer. Hemorrhage increases the measured infarct size to the point that it is actually larger than that seen with ligation alone. However, this increase is accounted for by the larger amount of intramyocardial hemorrhage. Hemorrhage is greatest in the center of the infarct and decreases at the margins. It appears that hemorrhage occurs into necrotic muscle and does not occur significantly at the margins of the infarct where damage to otherwise viable myocardium might result.