Benzylated 1,2,3-triazoles as anticoccidiostats.

Substituted 5-amino-4-carbamoyl-1,2,3-triazoles 3a-w were prepared by two synthetic schemes and evaluated in vivo for anticoccidial activity. Both schemes proceeded by brominating appropriately substituted toluenes 4a-s,v to 5a-s,v. In Scheme I, the brominated benzyl analogues 5 were converted to the corresponding benzyl azides 6, which were treated with cyanoacetamide to yield 1-substituted-5-amino-4-carbamoyl-1,2,3-triazoles 3. In Scheme II, the benzyl halides 5 were employed to alkylate the sodium salt of 5-amino-4-carbamoyl-1,2,3-triazole (7). Preliminary screening data against Eimeria acervulina and E. tenella in chickens suggested structural requirements for maximizing activity. Further evaluation against a relatively resistant series of eight Eimeria field isolates revealed L-651,582 (3a) to be a highly effective coccidiostat. However, unacceptable tissue residues precluded further development. Mechanistic studies on this series of 5-amino-4-carbamoyl-1,2,3-triazoles and, in particular, on L-651,582 (3a) revealed that its mode of action does not involve inhibition of IMP dehydrogenase, but probably interferes with host cell calcium entry. In addition, L-651,582 has been found to have antiproliferative activity in several disease models and was recently reported to possess antimetastatic activity in a model of ovarian cancer progression.

1-(substituted)benzyl-5-aminoimidazole-4-carboxamides are potent orally active inhibitors of Trypanosoma cruzi in mice.

1-(Substituted)benzyl-5-aminoimidazole-4-carboxamides are potent orally active inhibitors of Trypanosoma cruzi infections in mice. The most active compounds are the 1-(4-chlorobenzyl)- and 1-(3,4-dichlorobenzyl)-analogs (L-153,094 [2] and L-153,153 [4], resp.) which are approximately 7-fold more potent upon oral administration than nifurtimox (Lampit) in suppressing parasite levels in the blood of mice with acute Trypanosoma cruzi infections.

Relation of blood pressure during exercise to anaerobic metabolism.

To determine the effects of anaerobic metabolism on blood pressure (BP), 25 subjects were studied for BP response to graded and continuous leg-crank ergometry under both aerobic and anaerobic conditions. Measurements obtained during exercise also included ventilatory equivalents for oxygen and carbon dioxide to determine anaerobic threshold. Systolic and diastolic BP responses to exercise before anaerobic threshold were compared with responses after anaerobic threshold by linear regression analyses. The systolic BP response to graded exercise was significantly accelerated (p less than 0.01) after anaerobic threshold, demonstrating a nonlinear response to proportionately graded exercise demand. Comparison of the slopes or rates of change in diastolic BP before and after anaerobic threshold also indicated a significant difference (p less than 0.01) under these 2 different metabolic conditions. It is concluded that in contrast to the linear response of BP under conditions of aerobic metabolism, BP responds nonlinearly during anaerobic metabolism.

Fine specificity, structure, and proteolytic susceptibility of the human lymphocyte receptor for IgE.

Properties of the Fc receptor for IgE (FC epsilon R) on cultured human B lymphoblastoid cells (RPMI 8866) were studied. Specificity for human IgE (hIgE) was demonstrated by inhibition studies with both Fc epsilon R+ intact cell and detergent-solubilized receptor preparations. No interaction of the FC epsilon R with other hIg classes or with rodent IgE was seen. In other studies, 3,3-dithiobis(sulfosuccinimidyl) propionate was used to cross-link hIgE to 125I surface-labeled 8866 cells. After detergent solubilization, the 125I receptor components were isolated by immunoprecipitation, and receptor peptides of 83 and 46 kilodalton kD were demonstrated by SDS-PAGE in the presence of reducing agents. Cross-linking performed after detergent solubilization gave identical results. Tryptic maps of the 83 and 46 kD polypeptides were identical with respect to surface-iodinated peptides; this indicates a structural homology between these components. The 83 kD component was more difficult to elute from IgE affinity columns, potentially because of an increased number of IgE binding sites per FC epsilon R molecule. Limited proteolysis studies of the purified FC epsilon R with papain and V8 protease from Staphylococcus aureus demonstrated that a 16 kD FC epsilon R fragment was rapidly produced. This component was also seen after papain treatment of intact cells, and it retained the ability to interact with anti-FC epsilon R antisera and, at least in the absence of detergent, with hIgE affinity columns. Potential relationships between the FC epsilon R and lymphokines that modulate the IgE response (IgE-binding factors) are discussed.

The murine lymphocyte receptor for IgE. I. Isolation and characterization of the murine B cell Fc epsilon receptor and comparison with Fc epsilon receptors from rat and human.

The Fc receptor for IgE (Fc epsilon R) on murine B lymphocytes was studied by using BALB/c mice infected 12 to 18 days previously with Nippostrongylus brasiliensis. B cells were enriched in the Sephadex G-10-passed lymphocytes by treating with anti-Thy-1.2 and complement (C). After stripping any cytophilic Ig with low pH, the B cells were 125I surface labeled; subsequently the membranes were solubilized with nonionic detergent, and putative Fc epsilon R components were allowed to bind to IgE-coated adsorbents. Bound radiolabel was eluted with low pH, and when examined by SDS-PAGE, was found to consist primarily of a relatively broad band centered at 49,000 m.w. (49K). Fluid-phase IgE could prevent the binding of the 49K component to the IgE solid-phase adsorbents. Rebinding studies further indicated that the 49K component exhibited a specificity for IgE, thus confirming that the 49K component was the murine B lymphocyte Fc receptor for IgE (Fc epsilon R). Some rebinding to rabbit IgG was observed, and by using 2.4G2, the monoclonal anti-Fc gamma 2b receptor (Fc gamma 2bR) antibody to isolate the IgG2b receptor, a clear distinction between the FC gamma 2bR and the 49K IgE receptor was demonstrated by SDS-PAGE analysis. Rabbit IgG was thus found to interact with both the 49K Fc epsilon R and the 59K FC gamma 2bR. The murine B lymphocyte Fc epsilon R was compared with the human B cell Fc epsilon R from the RPMI 8866 cell line and with the high affinity Fc epsilon R on rat basophilic leukemia cells by one- and two-dimensional gel analyses. The lymphocyte Fc epsilon R from mouse and human was found to be quite similar with respect to m.w. (45 to 50K) and isoelectric point (pI 4.5 to 5.0), whereas the basophil Fc epsilon R differed in both aspects.

Ivermectin, a new broad-spectrum antiparasitic agent.

22,23-Dihydroavermectin B1, ivermectin, derived from avermectin B1 by selective hydrogenation using Wilkinson's homogenous catalyst [Ph3P)3RhCl], was shown to be a highly effective drug for the treatment of a wide variety of metazoan parasitic diseases in animals.

Diet-related macular anomalies in monkeys.

Fundus color photographs and retinal fluorescein angiograms were obtained from 48 nonhuman primates of three macaque species. Yellow pigmentation of the macula was present in monkeys fed a standard laboratory diet containing xanthophylls but was absent in animals maintained on semipurified or liquid formula diets with no xanthophyll content. Plasma levels of xanthophylls ranged from 0.5 to 2.4 microliters/ml in monkeys receiving the standard diet but were undetectable in animals raised on semipurified or liquid formula diets. Fluorescein angiograms revealed foveal areas of hyperfluorescence in almost all monkeys; however, the degree of hyperfluorescence was significantly greater in monkeys maintained on the semipurified or liquid formula diets.

Methyl 6-(phenylsulfinyl)imidazo[1,2-a]pyridine-2-carbamate, a potent, new anthelmintic.

A series of methyl imidazo-[11,2-a]pyridine-2-carbamates was synthesized for anthelmintic testing. The preparation of this class of compounds was simplified by utilization of a novel one-step condensation of the appropriately substituted 2-aminopyridine and methyl chloroacetylcarbamate. The most potent compound, methyl 6-(phenylsulfinyl)-imidazo[1,2-a]pyridine-2-carbamate, was orally effective against a broad range of helminths in sheep and cattle, at a dosage of 2.5 mg/kg. Limited trials in swine and dogs demonstrated anthelmintic activity at higher dosages. Limited observations in sheep and cattle indicated that, in both species, a single oral dose of 200 mg/kg was well tolerated.

Direct effect of physiological doses of arginine vasopressin on the arterial wall in vivo.

Effects of topically applied arginine vasopressin (VPA), in 100-150 muU/ml blood concentration, on external diameter (D) and on dynamic elastic modulus (E*) of surgically denervated common carotid (CC) and femoral (FA) arteries have been studied before and after hypophysectomy in anesthetized dogs. Changes in D, E*, and flow resistance (R) of the CC and FA vascular beds before and after removal of the pituitary were also determined. It was found that VPA elicited a substantial (max 21-26%) decrease in E* and a smaller (max 5.9-6.9%) reduction in D of FA independent of the presence of absence of the pituitary gland. The VPA effect developed more rapidly after hypophysectomy than before. In the CC, VPA did not significantly affect values of E*. During the 1-h period after hypophysectomy, statistically significant decreases in E*-CC, E*-FA, and D-CC were observed, but D-FA did not change, although arterial pressure as well as R-FA and R-CC were diminished. These results give further support to physiological vascular actions of VPA and a possible role in short-term circulatory control. In large arteries, the effects of VPA also seem to be regionally differentiated.

4-amino-6-(trichloroethenyl)-1,3-benzenedisulfonamide, a new, potent fasciolicide.

The synthesis and fasciolicidal activity of 4-amino-6-(trichloroethenyl)-1,3-benzenedisulfonamide are reported. A single dose of 15 mg/kg was effective in removing over 90% of immature Fasciola hepatica from sheep (6 weeks after infection) and calves (8 weeks after infection). A 2.5 mg/kg dose removed over 90% of mature (16 weeks old) liver fluke from sheep. Single oral doses up to 400 mg/kg were tolerated by sheep without gross toxic symptoms.

Hemodynamic responses to stellate ganglion stimulation in mongrels and greyhounds.

A comparison of the effects of left stellate ganglion stimulation (SGS) on central and aortic hemodynamics has been made in chloralose-anesthetized mongrel (M), and greyhound (GH) dogs. Measurements of aortic pressure and flow, and left ventricular pressure were made during stimulation of the decentralized left SG at different frequencies from 0 to 20 Hz. The increases in aortic pressure and flow with SGS were larger in the GH, especially for low frequencies of stimulation. Stroke volume was increased with SGS in the GH at all stimulation rates, whereas in the M it was unchanged. A greater decrease in left ventricular end-diastolic pressure with SGS was found in the GH. These results suggest that differences exist in both the intrinsic and extrinsic control of cardiac output in the greyhound dog compared to the mongrel. These differences may be in part responsible for the elevated arterial blood pressure in the greyhound compared to the mongrel.

Comparison of arterial hemodynamics in the mongrel dog and the racing greyhound.

This study was undertaken to define certain differences in cardiovascular function between mongrel (M) and greyhound (GH) dogs. In unanesthetized, trained, chronically instrumented animals mean arterial pressure was significantly higher in the GH (118 vs. 98 mmHg). This was associated with a significantly higher cardiac index in the GH (4.3 vs 3.1 liters/min per m2) and a lower calculated peripheral resistance. Central venous renin activity was significantly lower in the GH when unanesthetized (1.51 vs. 2.88 ng/ml per h). Values of vascular impedance at several selected arterial sites were lower in the GH compared to the M, suggesting differences in arterial wall mechanical properties. The hydraulic power delivered to the aorta by the left ventricle in the GH was twice that of the M (1,166 vs. 564 mol wt). Oscillatory power represented a greater fraction of total aortic power in the GH (15.7 vs. 10.8%). Differences were also observed in the hemodynamic response to acute pentobarbital anesthesia. Thus the young adult GH is hemodynamically different from its mongrel counterpart. These differences bear some resemblance to hemodynamic changes seen in various types of experimental hypertension in animals and to those observed in the early phase of essential hypertension in man.

Effects of carotid hypotension on aortic hemodynamics in the unanesthetized dog.

The effects of occlusion of the brachiocephalic artery on aortic hemodynamics were assessed in 12 chronically instrumented dogs in the unanesthetized state. Continuous measurements of ascending aorta pressure and flow were made. In the steady state following occlusion, heart rate increased by 36% and mean arterial pressure by 45%, while cardiac output was unchanged from preocclusion levels. Hydraulic power delivery to the systemic circulation by the left ventricle was increased during occlusion, while the fraction of total power associated with pulsations decreased. Values of peripheral resistance and ascending aorta input impedance were both increased during occlusion. Graded occlusions of the brachiocephalic artery produced graded, monotonic increases in the entire aortic impedance spectrum between 2 and 20 Hz with more sensitive responses occurring with the smaller, submaximal responses. Considered with results of previous studies, these results suggest that activation of smooth muscle in large conduit arteries is also associated with the pressor response which accompanies carotid hypotension and that such activation has a hemodynamically significant effect.