The blood cells of the pulmonate snail Biomphalaria tenagophila, an important transmitter of the trematode Schistosoma mansoni in Brazil, were examined by light and transmission electron microscopy (TEM). Two hemocyte types were identified: hyalinocytes and granulocytes. Hyalinocytes are small young (immature), poorly spreading cells, which have a high nucleocytoplasmic ratio and are especially rich in free ribosomes. They do not appear to contain lysosome-like bodies and represent less than 10% of the circulating hemocytes. Granulocytes are larger hemocytes which readily spread on glass surface and which strongly react to the Gomori substrate, indicating the enzyme acid phosphatase usually found in lysosomes. Ultra-structurally, they contain a well-developed rough endoplasmic reticulum, dictyosomes and some lysosome-like dense bodies. Granulocytes do not exhibit a characteristic granular aspect and the few granules observed in the cytoplasm should correspond to a lysosome system. They were named granulocytes instead of amoebocytes to use the same terminology adopted for Biomphalaria glabrata in order to make easier comparative studies. This is a preface study for more specific investigations on the functional activities of the blood cells of B. tenagophila and their interactions with the trematode parasite.

No abstract

The leaves of guaco (Mikania glomerata and M. laevigata) are widely used for the treatment of asthma and bronchitis. An LC method for the quantification of coumarin and O-coumaric acid in medicinal extracts was developed and validated for linearity, limit of detection, accuracy, precision, as well as intra- and inter-day variations. Extracts and isolated markers were tested in the mice allergic pneumonitis model and the histopathological profile of the lung tissue was analysed. The values found for coumarin and O-coumaric acid in a fluid extract were 1.53 and 1.69 mg/mL, respectively, for M. glomerata, and 0.96 and 0.38 mg/mL for M. laevigata. The values found for the lyophilised aqueous extract were 0.22 and 0.11 mg/mL of coumarin and O-coumaric acid in M. glomerata and 0.05 and 0.02 mg/mL in M. laevigata, respectively . The analysed samples from the species M. glomerata presented more coumarin and O-coumaric acid than the analogous M. laevigata species. Both coumarin and O-coumaric acid are part of the phytocomplex which is responsible for the therapeutic activity of the guaco species. The lyophilisation process generated some alterations in the extract, in comparison with the fresh aqueous extract, and these extracts did not present anti-inflammatory activity. Comparing the histopathological images of the groups tested, a haemorrhagic profile of lung tissue of animals treated with lyophilised extract, O-coumaric acid and coumarin is observed, but not for the group treated with hydroalcoholic extract. It is probable that some protective effect of the whole extract (lost during the lyophilisation process) blocks the harmful effects of the isolated markers.

1 The effector mechanism of intestinal necrosis in rat anaphylaxis was studied following several complementary approaches: (i) the use of monoclonal antibodies (mAb) belonging to different classes (IgGl, IgG2b and IgE anti-DNP), (ii) the assay of mediators, and (iii) the use of pharmacological tools. 2 Lethality and haemorrhagic necrosis of the small intestine were observed in IgE-sensitized rats, whereas IgG mAb produced milder physiological disturbances. 3 Inhibition of leukotriene biosynthesis reduced the drop of systemic blood pressure (BP) and the extent of protein-rich plasma exudation but it did not influence the haemorrhagic component of intestinal necrosis. 4 The antihistamine, pyrilamine, partially diminished the haemorrhagic component of the intestinal necrosis.5 The involvement of mediators related to platelet-activating factor (PAF) was studied by examining the pharmacological effects of these autacoids and of PAF-receptor antagonists (PCA4248, UR12460 and BB823). PAF induced intestinal lesions similar to those observed in IgE-sensitized rats and PAF-receptor antagonists markedly decreased haemorrhage in IgE-sensitized rats. 6 PAF levels were transiently increased after dinitrophenol (DNP)-bovine serum albumin (BSA) challenge in the small intestine of IgE-sensitized rats. 7 These data stress differences in the outcome of anaphylaxis related to the type of receptors for the Fc portion of immunoglobulins that are involved. IgE is the antibody class that elicits the most severe response due to the activation of mast cells via FceRI (surface receptors that bind IgE antibodies with high affinity), and the only one able to produce intestinal haemorrhagic necrosis. 8 The mast-cell-derived mediators PAF/acyl-PAF and histamine, most probably associated with tumour necrosis factor a/cachectin (TNF-x), seem to play a central role in the production of the vascular changes required for the extravasation of erythrocytes in the small intestine mucosa.

These results show important modulatory effects of bradykinin B(1) and B(2) receptor antagonists in both models of lung inflammation.

No abstract

1 The involvement of platelet-activating factor (PAF) in immune complex-induced/polymorphonuclearmediated tissue injury was studied by use of a reverse passive Arthus (RPA) model in the peritoneal cavity of rats. 2 Extravasation of protein-rich plasma, accumulation of polymorphonuclear leukocytes (PMN), and the production of nitric oxide (NO) by resident peritoneal mononuclear phagocytes were assayed. 3 Treatment of rats with either UR-12460 or BB-823, two compounds which possess different chemical structures, but elicit the same antagonistic effect on the PAF receptor, abrogated protein-rich plasma extravasation. In contrast, they did not show any effect on the accumulation of PMN. 4 Inhibition of NO production with both N1-mono methyl-L-arginine and N0-nitro-L-arginine failed to prevent protein-rich plasma extravasation. 5 The production of NO by peritoneal adherent cells following RPA was measured in cells maintained for 2 to 28 h in culture, and it was significantly increased in cells removed as early as 15 min after RPA induction, as compared to controls. 6 Addition of 10 nM PAF to the culture medium reduced the generation of NO by peritoneal cells from RPA rats, whereas this mediator enhanced NO production in cells from naive control animals. 7 Treatment with either UR-12460 or BB-823 prior to the induction of RPA produced an almost complete inhibition of NO production. 8 Assay of nitric oxide synthase activity in cell homogenates from peritoneal cells showed that the activity was due to the inducible form of the enzyme. 9 Study by Northen blotting of mRNA coding for the inducible NO synthase (iNOS) showed transcription at 6 and 18 h after the induction of RPA, which was inhibited in UR-12460-treated rats. 10 These data indicate that PAF is the main mediator of the early plasma leakage observed in RPA, and also that PAF is implicated in the triggering of long-term changes via induction of specific genes, as judged from its ability to promote the expression of iNOS.

No abstract