A selective inhibitor of thromboxane synthetase activity of rabbit heart tissue: a pyridazinic derivative

The effects of 2-(2 dimethylaminoethyl) 5-benzylidene 6-methyl (2H,4H)-3-pyridazinone (III) were studied on the biosynthesis of TXA2 and PGI2 in vitro the TXA2 and PGI2 synthetase activity of heart tissue. Biosyntheses of TXA2 and PGI2 were carried out using arachidonic acid as a substrate and horse platelet and aorta microsomes as sources of TXA2 and PGI2 synthetases respectively. TXB2 and 6-keto PGF1 alpha were determined by RIA. III--did not significantly modify either the biosynthesis of PGI2 in vitro or the PGI2 synthetase activity of heart tissue. did not significantly inhibit TXA2 biosynthesis in vitro but markedly reduced the TXA2 synthetase activity of heart tissue: for a microsomal fraction concentration of 100 micrograms protein, the ID50 was 6.37 X 10(-5) M +/- 1.29 X 10(-8) M. Thus III behaves as a specific inhibitor of the TXA2 synthetase activity of heart tissue and could have a beneficial use in therapeutics.     

Cellular differences in the regeneration of murine skeletal muscle: a quantitative histological study in SJL/J and BALB/c mice

Summary Skeletal muscle regeneration in SJL/J and BALB/c mice subjected to identical crush injuries is markedly different: in SJL/J mice myotubes almost completely replace damaged myofibres, whereas BALB/c mice develop fibrotic scar tissue and few myotubes. To determine the cellular changes which contribute to these differential responses to injury, samples of crushed tibialis anterior muscles taken from SJL/J and BALB/c mice between 1 and 10 days after injury were analysed by light and electron microscopy, and by autoradiography. Longitudinal muscle sections revealed about a 2-fold greater total mononuclear cell density in SJL/J than BALB/c mice at 2 to 3 days after injury. Electron micrographs identified a similar proportion of cell types at 3 days after injury. Autoradiographic studies showed that the proportions of replicating mononuclear cells in both strains were similar: therefore greater absolute numbers of cells (including muscle precursors and macrophages) were proliferating in SJL/J muscle. Removal of necrotic muscle debris in SJL/J mice was rapid and extensive, and by 6 to 8 days multinucleated myotubes occupied a large part of the lesion. By contrast, phagocytosis was less effective in BALB/c mice, myotube formation was minimal, and fibrotic tissue conspicuous. These data indicate that the increased mononuclear cell density, more efficient removal of necrotic muscle, together with a greater capacity for myotube formation in SJL/J mice, contribute to the more successful muscle regeneration seen after injury.     

Contrasting breeding systems in twoEriotheca (Bombacaceae) species of the Brazilian cerrados

The pollination biology and breeding systems ofEriotheca pubescens andE. gracilipes have been studied. These two species occur as trees in cerrado vegetation, the neotropical savannas of Central Brazil, with partially sympatric distributions. They have similar phenology and floral structure, although the flowers ofE. pubescens are larger. Both species have nectar flowers pollinated by largeAnthophoridae bees but the main pollinators of each species differ in size. The species have markedly different breeding systems: late-acting self-incompatibility inE. gracilipes and apomixis stimulated by pollination inE. pubescens.     

Mechanisms of protection against herpes simplex virus type 1-induced retinal necrosis by in vitro-activated T lymphocytes.

In BALB/c mice, acute retinal necrosis occurs in the uninoculated eye 8 to 10 days following uniocular anterior chamber inoculation of the KOS strain of herpes simplex virus type 1 (HSV-1). Retinitis in the uninjected eye can be prevented if HSV-1-specific immune effector cells that have been restimulated with virus in vitro are administered intravenously within 1 day of anterior chamber inoculation of virus. We explored further the mechanism of protection afforded by these activated immune effector cells. The results of our studies revealed that optimal protection from retinitis required in vitro restimulation, since infusion of 50 x 10(6) HSV-1-primed but nonrestimulated cells could not protect as well as 10 x 10(6) activated cells. Analysis of both restimulated and nonrestimulated cells showed that only in vitro-restimulated cells were cytotoxic to HSV-1-infected syngeneic target cells. From these studies, we concluded that the ability to kill virus-infected target cells contributed to optimal protection achieved by intravenous administration of activated immune effector cells. Furthermore, T-cell subset depletion of activated immune effector cells demonstrated that both L3T4+ and Lyt-2+ T cells in the transfer inoculum contributed to protection. Additional studies revealed that although the transferred immune effector cells reached the injected eye within 24 h, virus replication in the injected eye was not affected. In the uninjected eye, virus titers were low, consistent with protection of this eye from retinitis. Taken together, the virus recovery results suggest that the interaction of virus with intravenously administered HSV-1-specific immune effector cells which limits virus spread and/or replication of virus probably occurred within the central nervous system and prevented the second wave of virus from entering the uninoculated eye.     

Culture of soybean fruit explants: growth conditions and efficiency of nitrogen sources for reserve protein synthesis

A system was devised for the in vitro culture of soybean fruits. The culture system consisted of a single fruit attached to a short piece of stem through which the nutrients were supplied. The fruit explants were taken when pods were fully expanded and the seeds at initial stages of growth. During a 7-day culture period, the seeds accumulated dry matter and protein in quantities comparable to those in situ. Omission of the C source (sucrose) from the medium resulted in no dry matter accumulation in the seeds, but omission of the N source (glutamine) still led to some protein accumulation, indicating mobilization of N from other parts of the fruit explant. Optimum protein accumulation occurred when glutamine was supplied at 1.2 mg N ml^-1. Protein accumulation in the seeds was highly dependent on the nature of the N source. Glutamine, asparagine and the ureide, allantoin, were equally the most efficient sources, whereas several other amino acids tested showed lower degrees of efficiency. The data indicate a high metabolic capacity of the fruit tissues for principal N transport compounds of soybean, namely allantoin, asparagine and glutamine. The culture system described should prove useful for developmental and metabolic studies where the complex influence of the rest of the plant is to be avoided.Abbreviations ALN allantoin - ALC allantoic acid Preliminary report presented at the IV World Soybean Research Conference, Buenos Aires, Arggentina, March 1989.     

Leishmania mexicana amazonensis: Surface charge of amastigote and promastigote forms

The surface charge of Leishmania mexicana amazonensis was evaluated by means of the binding of colloidal iron hydroxyde particles at pH 1.8 and cationized ferritin particles at pH 7.2 to the cell surface, visualizated by electron microscopy and by direct measurements of the electrophoretic mobility of cells suspended in solutions of different pH. The following forms of the parasite were analysed: amastigotes (surrounded or not by the membrane of the endocytic vacuole, isolated from lesions), transitional forms, and infective (5 passages) and noninfective (176 passages) promastigotes. The results obtained indicate that the surface of L. m. amazonensis contains both negatively and positively charged dissociating groups and that changes occur in the surface charge during amastigote-promastigote transformation. Treatment of the parasite with neuraminidase significantly reduced the electrophoretic mobility of the cells. Neuraminidase-treated cells recovered their normal electrophoretic mobility when incubated for 8 hr in fresh culture medium by a process that is inhibited by puromycin.     

Antigenic relationships between Aracoccidioides loboi and other pathogenic fungi determined by immunofluorescence

Summary The fluorescent antibody technique was used to study antigenic relationships betweenParacoccidioides loboi and other pathogenic fungi. The findings suggest thatP. loboi is more closely related antigenically to certainP. brasiliensis strains than to others and that it has antigens in common with the yeast form ofHistoplasma capsulatum, H. duboisii, Blastomyces dermatitidis, Candida albicans and also the mycelial form ofCoccidioides immitis. Serum globulins from 3 cases of keloidal blastomycosis were labelled with fluorescein isothiocyanate. These conjugates showed slight or no reactivity withP. loboi, the yeast forms ofP. brasiliensis, H. capsulatum, H. duboisii andB. dermatitidis, However, they stained brightlyC. albicans, serotypes A and B, the tissue form ofC. immitis and the yeast form ofSporotrichum schenckii. Adsorption of these reagents withC. albicans eliminated all staining except that forS. schenckii. These patients had no history of clinical sporotrichosis.Deceased. Last address: Fundacão Gonçalo Moniz, Salvador, Bahia, Brazil. Requests for reprints should be sent to Dr.William Kaplan.Dr.Miranda is in private practice in Rio de Janeiro, Brazil.