Pulmonary vascular response of the coati to chronic hypoxia.

The unusually muscular pulmonary arteries normally present in cattle and swine residing at low altitude are associated with a rapid development of severe pulmonary hypertension when those animals are moved to high altitude. Because these species lack collateral ventilation, they appear to have an increased dependence on hypoxic vasoconstriction to maintain normal ventilation-perfusion balance, which, in turn, maintains thickened arterial walls. The only other species known to lack collateral ventilation is the coati, which, similarly, has thick-walled pulmonary arteries. We tested the hypothesis that coatis will develop severe high-altitude pulmonary hypertension by exposing six of these animals (Nasua narica) to a simulated altitude of 4,900 m for 6 wk. After the exposure, pulmonary arterial pressures were hardly elevated, right ventricular hypertrophy was minimal, there was no muscularization of pulmonary arterioles, and, most surprising of all, there was a decrease in medial thickness of muscular pulmonary arteries. These unexpected results break a consistent cross-species pattern in which animals with thick muscular pulmonary arteries at low altitude develop severe pulmonary hypertension at high altitude.

Activity of anticancer compounds against Trypanosoma cruzi-infected mice.

Chagas' disease, which is caused by Trypanosoma cruzi, remains essentially incurable. Due principally to a lack of profit incentive, the pharmaceutical industry has had limited interest in developing new antichagasic drugs. Thus, a search for agents that exhibit activity against T. cruzi, although medicaments have been developed for the treatment of other diseases, seems justifiable. Responding to evidence that the principal biochemical differences between mammalian cells and African trypanosomes apply equally to T. cruzi, our evaluations were conducted. Previous work showed the effectiveness of anticancer agents against T. rhodesiense. In the present studies, 76 anticancer compounds were assessed for their ability to suppress the trypomastigotes of T. cruzi- infected mice. Five compounds were found to be active. The most effective was cycloheximide, which was more than six times as effective as the standard, nifurtimox.

In pursuit of drugs for American trypanosomiasis: evaluation of some "standards" in a mouse model.

Forty-nine "standard" compounds known to be useful in the treatment of other diseases were tested for their suppressive activity against the trypomastigotes of Trypanosoma cruzi-infected mice. The most active was the antidepressant protriptyline, which was almost three times as effective as the reference drug, nifurtimox. A major value of the present data is to demonstrate the refractoriness of the T. cruzi parasite against many of the drug standards that have known biological activity.

Chagas' disease: a search for treatment and a question--should the disease be of military concern?

If military forces are required to operate in areas that are endemic for Chagas' disease, the occupation should be of critical concern. These areas, located in Central and South America, are many. The matter is of particular importance because no suitable drug exists to treat individuals who contract the disease. We examined 60 compounds of a chemical class, thiosemicarbazones, known to have some activity against the disease. The work was carried out using Trypanosoma cruzi-infected mice. Of the 60 potential drugs evaluated, 12 showed significant suppressive activity. One of these compounds was almost 50% greater than the reference drug used in the test system.

CP-0597, a selective bradykinin B2 receptor antagonist, inhibits brain injury in a rat model of reversible middle cerebral artery occlusion.

BACKGROUND AND PURPOSE: Recent studies demonstrated a significant neuroprotective action of the selective peptide-based bradykinin B2 receptor antagonist CP-0597 after permanent middle cerebral artery (MCA) occlusion (MCAO) in the rat. We therefore evaluated the efficacy of this compound after reversible MCAO in the rat. METHODS: Male Wistar rats underwent reversible MCAO by insertion of a nylon monofilament to the origin of the MCA. After 1 hour the filament was retracted and the ischemic tissue reperfused. Immediately after MCAO, primed miniosmotic pumps containing either vehicle or CP-0597 (300 ng/kg per minute) were implanted into the subcutaneous space (n = 14 per group). Twenty-four hours after surgery, animals were killed and brains fixed, and 4-micron sections were taken from five sequential tissue blocks labeled A through E and stained with hematoxylin and eosin. Clinical evaluation of rats was performed by neurological scoring and change in body weight. RESULTS: Treatment with CP-0597 significantly reduced percent increase in hemisphere size of the ischemic hemisphere in all brain sections (C section: vehicle, 40.6 +/- 4.3% versus CP-0597, 20.8 +/- 5.3%; P < 0.001), total infarct volume (vehicle, 206.5 +/- 7.7 mm3 versus CP-0597, 94.0 +/- 19.2 mm3; P < .001), cortical infarct volume (vehicle, 145.5 +/- 4.5 mm3 versus CP-0597, 64.0 +/- 15.1 mm3; P < .001), subcortical infarct volume (vehicle, 55.8 +/- 4.1 mm3 versus CP-0597, 27.5 +/- 4.5 mm3; P < .001), and the number of necrotic neurons (vehicle 42.9 +/- 3.8 versus CP-0597, 23.6 +/- 4.7 per field; P < .01). Neurological score (vehicle, 2.78 +/- 0.36 versus CP-0597, 6.29 +/- 0.87 P < .01) and change in body weight (vehicle, -28.7 +/- 2.0 g versus CP-0597, -18.2 +/- 2.8 g; P < .01) were also significantly improved. CONCLUSIONS: The present data demonstrate the significant overall efficacy profile of CP-0597 in a rat model of reversible MCAO and provide strong rationale for the use of such bradykinin B2 receptor antagonist in the treatment of stroke.

Potent, long-acting, orally-active bradykinin antagonists for a wide range of applications.

Actions of bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg; BK) are mediated by constitutively expressed B2 receptors, that require the full BK peptide chain, and by B1 receptors, induced in inflammation, that use BK(1-8) as ligand. In addition to many physiological and pathophysiological functions, the growth factor activity of BK evidently allows it to act as an autocrine stimulant for small cell lung cancer. A new group of BK antagonists containing the novel amino acid a-(2-indanyl)glycine provides extremely potent broad-spectrum as well as selective antagonists for all these functions.

Oral activity of peptide bradykinin antagonists following intragastric administration in the rat.

This study has investigated the oral activity, following intragastric administration, of three potent and long-acting peptide-based bradykinin antagonists, HOE-140, B9430, and CP-0597, in the anesthetized rat, using bradykinin-induced hypotension. Two of the three bradykinin antagonists, B9430 and HOE-140, but not CP-0597, were found to be active following intragastric administration, producing dose-dependent (1, 3, and 10 mg/kg) and selective inhibition of bradykinin-induced hypotension. At a dose of 10 mg/kg, the inhibition of bradykinin-induced hypotension occurred within 15 min and lasted for at least 2 h, which was the duration of the experiment. HOE-140 and CP-0597, 10 micrograms/kg i.v., produced significant inhibition of bradykinin-induced responses that lasted for 60 min. B9430, 10 micrograms/kg i.v., produced a significantly greater inhibition than HOE-140 and CP-0597, this inhibition being significant for the duration of the experiment (2 h) compared with saline controls. Considering the close chemical structure of CP-0597 compared with HOE-140 and B9430, it is not clear as to why CP-0597 was inactive via the intragastric route. This is the first demonstration of the oral activity of peptide-based bradykinin antagonists following intragastric administration in the rat.

Potent, long-acting bradykinin antagonists for a wide range of applications.

Actions of bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg; BK) are mediated by constitutively expressed B2 receptors (which require the full BK peptide chain) and by B1 receptors (which require BK (1-8) as ligand) that are induced in inflammation. BK has many functions in normal and pathological physiology, including initiation of most, if not all, inflammation. BK also evidently functions as an autocrine stimulant for growth of small cell lung cancer (SCLC). A new group of BK antagonists containing the novel amino acid alpha-(2-indanyl)glycine (Igl) provides both broad-spectrum and selective antagonists for all these functions. As examples, D-Arg-Arg-Pro-Hyp-Gly-Igl-Ser-D-Igl-Oic-Arg (B9430) is an extremely potent and long-acting antagonist of both B1 and B2 receptors, is stable against endogeneous kininase enzymes, and is active in various in vivo models, including by intragastric administration. Acylation of B9430 with dehydroquinuclidine-2-carboxylic acid (Dhq) gives B9562, a highly selective B2 antagonist. In contrast, Lys-Lys-Arg-Pro-Hyp-Gly-Igl-Ser-D-Igl-Oic (B9858) is a highly potent and selective B1 antagonist. The dimer of B9430 linked at the amino terminus with suberimide is a potent selectively cytotoxic agent for SCLC cells. Results with these peptides suggest that a new generation of antiinflammatory and anticancer drugs may be at hand.

Evidence that certain 8-aminoquinolines are potentially effective drugs against Chagas disease.

Forty 8-aminoquinolines (a chemical class with members having some activity against Trypanosoma cruzi infections) were evaluated for their effectiveness in reducing the 14-day parasitaemias of 4-6 week-old, female, albino mice infected with a Brazilian strain of T. cruzi. Six of the compounds were more active or as active as the reference drug, nifurtimox, and one was > 13-fold as efficacious. Certain members of the series tested warrant further evaluation.

Primaquine analogues that are potent anti-Trypanosoma cruzi agents in a mouse model.

Seventy-seven primaquine analogues were evaluated for their effectiveness in reducing the parasitaemias in female albino mice (aged 4-6 weeks) which had been infected with a Brazilian strain of Trypanosoma cruzi 15 days earlier. Of the analogues tested, 23 were more effective than the reference drug, nifurtimox, and one was > 14-fold as effective as the standard and almost four times as active as primaquine itself. Certain members of the series tested warrant further evaluation.

Pulmonary capillary recruitment in neonatal lambs.

In species having lungs large enough to develop hydrostatic perfusion zones, increased pulmonary arterial pressure causes blood flow to be redistributed from the lower to the upper lung. The blood flow increase in the upper lung recruits capillaries and increases gas exchange surface area. There is disagreement, however, about whether such capillary recruitment occurs in young animals with small lungs. To investigate this issue, we used in vivo microscopy to directly study capillary perfusion in individual alveolar walls in the upper lungs of neonatal lambs and in older lambs with larger lungs. Pulmonary arterial pressure was elevated by airway hypoxia. In neonatal lambs (< 10 d old; n = 7), hypoxia increased pulmonary arterial pressure by 55% but did not cause capillary recruitment. In older lambs (20-61 d old; n = 6), hypoxia increased pulmonary arterial pressure by 40% and caused a 46% increase in recruited capillaries. These results support the hypothesis that capillary recruitment does not occur in newborn lambs when pulmonary arterial pressure increases and implies that there is limited gas exchange reserve. In older lambs, however, gas exchange reserve develops through recruitable capillaries as the lungs mature.

Collateral ventilation and pulmonary arterial smooth muscle in the coati.

Collateral ventilation can participate in ventilation-perfusion regulation by shifting normoxic gas into hypoxic lung regions. In species lacking collateral pathways, such as cattle and swine, ventilation-perfusion balance must rely heavily on hypoxic vasoconstriction, which may explain why their muscular pulmonary arteries are much thicker than those of other animal species. The presence of these unusually muscular vessels in turn may account for the vigorous pressor response to acute hypoxia in these species. The only other species known to lack collateral ventilation is the coati. To determine whether coatis fit the pulmonary circulatory pattern of cattle and swine, we measured pulmonary arterial wall dimensions and pulmonary vascular responsiveness to acute airway hypoxia in 11 adult coatis. Hypoxia caused impressive pulmonary arterial hypertension [normoxia = 17 +/- 1 (SE) Torr, hypoxia = 40 +/- 2 Torr, cardiac output unchanged]. The medial thickness of muscular pulmonary arteries (50-300 microns) was 17.1 +/- 1.8% (SD) of external diameter, a thickness unprecedented in normotensive adult mammals. We conclude that coatis fit the pattern of other species lacking collateral ventilation, since they have thick-walled pulmonary arteries and a vigorous pressor response to hypoxia.

Determination of virulence and pathogenesis of a canine strain of Leishmania leishmania infantum in hamsters and dogs.

Visceral leishmaniasis was experimentally induced in hamsters by the intracardiac inoculation of 10(7) amastigotes of Leishmania leishmania infantum of canine origin. At postinoculation (PI) days 7, 21, 42, and 63, hamsters were euthanatized. Body weights and total parasite numbers of the liver and spleen were determined. Gross and histologic evaluations of tissues were done. Dogs also were inoculated IV with 10(8) amastigotes/kg of body weight. Samples were obtained from dogs prior to infection and at biweekly PI intervals for CBC and serum chemical analysis, for lymphocyte blastogenic assay by use of blood leukocytes, and for ELISA to determine antileishmanial antibody titers. At PI week 12, dogs were necropsied; organ weights, tissue imprints of the liver and spleen, and histologic interpretations of tissues were obtained. Hamsters developed high parasite numbers within 7 days after inoculation, at which time the total parasite numbers in the liver (3.51 x 10(7) amastigotes) was observed to be approximately 11 times that in the spleen (2.93 x 10(6)). The liver had the highest parasite numbers throughout the infection period. Some infected hamsters became either cachectic and emaciated or ascitic. Two of the 10 infected hamsters died at PI days 54 and 58. Moderate to severe hepatosplenomegaly with granulomatous inflammatory reactions characterized by the presence of varied numbers of parasitized macrophages, giant cells, and hepatic Schaumann bodies were observed in infected hamsters. Infected dogs developed significantly altered hematologic values consisting of mild anemia and moderate leukopenia at PI weeks 8 to 12. Hyperproteinemia characterized by hyperglobulinemia (4.5 g/dl) was noticed at PI week 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Activity of amphotericin B cholesterol dispersion (Amphocil) in experimental visceral leishmaniasis.

Standard therapy of human visceral leishmaniasis with parenteral pentavalent antimonial agents is generally curative but has the disadvantages of a 28-day treatment course, occasional treatment failures, and toxicity. The antifungal and antileishmanial agent amphotericin B has been complexed with lipids to develop a less toxic formulation of amphotericin B. Because lipid particles are phagocytized by the reticuloendothelial system, lipid-associated amphotericin B should be concentrated in infected macrophages and be very effective against visceral leishmaniasis. One formulation, amphotericin B cholesterol dispersion (ABCD) (Amphocil), was tested for antileishmanial activity in Leishmania donovani-infected hamsters. In the first experiment, hamsters were infected, administered with the drug 3 days later, and then sacrificed after a further 4 days. ABCD (dose needed to suppress 99% of hepatic parasites compared with controls [SD (99)], 0.4 mg/kg of body weight) was 15 times as effective as conventional amphotericin B [SD (99), 6.0 mg/kg]. Pentavalent antimony in the form of meglumine antimonate had an SD (84) of 416 mg/kg. In a second experiment in which animals were allowed to become more heavily infected, the drug was administered 10 days after infection and the animals were sacrificed after a further 2, 7, or 11 days. ABCD was approximately four times as active as conventional amphotericin B. These experiments suggest that ABCD is at least four times as active as conventional amphotericin B against visceral leishmaniasis and that clinical trials are warranted.

Development of Leishmania (Viannia) panamensis lesions and relationship of numbers of amastigotes to lesion area on antimony-treated and untreated hamsters.

Young adult (60-70-g) male golden hamsters (Mesocricetus auratus) each were injected intradermally at the dorsal base of the tail with 15 x 10(6) promastigotes of Leishmania (Viannia) panamensis (MHOM/PA/83/WR539), and progression and regression of subsequent lesions were evaluated for up to 17 wk postinfection (PI) as to area, weight, and number of amastigotes within lesions in untreated hamsters and in hamsters treated with meglumine antimoniate (Glucantime). In untreated hamsters total area of lesion, weight, and numbers of amastigotes generally increased rapidly and concomitantly up to 3-4 wk PI. Amastigote numbers tended to decrease from 4 to 11 wk PI and subsequently the numbers of amastigotes within the lesions decreased rapidly, whereas relatively little change occurred in the area and weight of the lesions. Meglumine antimoniate treatment of cutaneous hamster lesions resulted in marked concomitant decrease in size of the lesions and numbers of amastigotes within the lesions examined 1 wk after treatment. Measurement of the area of cutaneous leishmanial lesions thus would appear to be a valid method of evaluating the efficacy of promising compounds against L. panamensis in hamsters when measurements are taken 3-5 wk after experimental infection and reflects the number of amastigotes present in the lesion.

Neutrophil kinetics in the pulmonary microcirculation during acute inflammation.

The site of neutrophil interaction with the vasculature during acute lung inflammation is controversial, but has been suggested to occur in the alveolar capillaries, in contrast with its location in postcapillary venules in nonpulmonary tissues. We studied the kinetics of neutrophil accumulation and the site of neutrophil-vascular interaction in the lung by examining directly the behavior of fluorescein isothiocyanate-labeled canine neutrophils utilizing in vivo fluorescence videomicroscopy through a window inserted into the chest wall of anesthetized dogs. The administration of fragments of the fifth component of complement (C5f) into either the airway or pulmonary artery resulted in neutrophil sequestration almost exclusively in pulmonary capillaries. Kinetically, there was a shift in the distribution of neutrophil transit times resulting in a marked prolongation of median transit time. This response occurred within seconds after intravascular C5f and within 5 minutes after airway C5f and was maintained for at least 30 minutes. Ultrastructural studies after airway C5f showed neutrophils in various stages of migration through the alveolar-capillary membrane and more than 90% of these neutrophils were seen to migrate from capillary rather than from venular sites. These data indicate that pulmonary inflammation differs from inflammation in other vascular beds primarily in the site of neutrophil localization and migration. This fundamental difference in the inflammatory response may serve to localize the inflammatory response to the alveolus, and (since cells were retained singly), indicates the inability of leukoaggregation adequately to explain the findings. Leukocyte accumulation in the lung may thus occur through alterations in the balance between delivery of neutrophils to the lung and the transit time of these cells across the capillary bed.

Flow through zone 1 lungs utilizes alveolar corner vessels.

We have previously observed flows equivalent to 15% of the resting cardiac output of rabbits occurring through isolated lungs that were completely in zone 1. To distinguish between alveolar corner vessels and alveolar septal vessels as a possible zone 1 pathway, we made in vivo microscopic observations of the subpleural alveolar capillaries in five anesthetized dogs. Videomicroscopic recordings were made via a transparent thoracic window with the animal in the right lateral position. From recordings of the uppermost surface of the left lung, alveolar septal and corner vessels were classified depending on whether they were located within or between alveoli, respectively. Observations were made with various levels of positive end-expiratory pressure (PEEP) applied only to the left lung via a double-lumen endotracheal tube. Consistent with convention, flow through septal vessels stopped when PEEP was raised to the mean pulmonary arterial pressure (the zone 1-zone 2 border). However, flow through alveolar corner vessels continued until PEEP was 8-16 cmH2O greater than mean pulmonary arterial pressure (8-16 cm into zone 1). These direct observations support the idea that alveolar corner vessels rather than patent septal vessels provide the pathway for blood flow under zone 1 conditions.

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.