Conceição R.S. Machado

Differential tissue distribution of diverse clones of Trypanosoma cruzi in infected mice

Chagas disease, caused by the protozoan Trypanosoma cruzi, presents variable clinical course but the phenomena underlying this variability remain largely unknown. T. cruzi has a clonal population structure and infecting strains are often multiclonal. T. cruzi genetic variability could be a determinant of differential tissue tropism or distribution and consequently of the clinical forms of the disease. We tested this hypothesis by using low-stringency single specific primer polymerase chain reaction (LSSP-PCR) to type genetically the parasites in tissues of experimental infected mice. BALB/c mice were simultaneously inoculated with two different T. cruzi populations (JG strain and Coll.7G2 clone). Doubly infected animals showed clear differential tissue distribution for the two populations (chronic phase). Our results indicate a significant influence of the genetic polymorphism of infecting T. cruzi populations in the pathogenesis of chronic Chagas disease.

Evidence for a direct action of Tityus serrulatus scorpion venom on the cardiac muscle

The ability of toxins to activate the cardiovascular system plays an important role in the morbidity and lethality of the Tityus serrulatus scorpion envenoming. Most of the actions of the scorpion toxins are indirect and due to the release of adrenergic and cholinergic neurotransmitters. Accordingly, treatment following envenoming is targeted towards inhibition of adrenergic and cholinergic receptors. Here, we have sought evidence for a direct action of T. serrulatus venom on the isolated rat heart (Langendorffs method). We show that the bradycardia induced by T. serrulatus venom was completely blocked by atropine, a muscarinic receptor antagonist. Similarly, the increase in heart rate that follows the venom-induced bradycardia was totally inhibited by a beta(1)-adrenoceptor antagonist or by chemical sympathetic denervation with 6-hydroxydopamine. In contrast to these findings, the venom-induced increase in contractile force was not modified by beta(1)-adrenoceptor blockade or by chemical sympathetic denervation. The results clearly demonstrate that the chronotropic effects of T. serrulatus are dependent on neurotransmitter release, but the inotropic effects are not. The neurotransmitter-independent increase in contractility seems to be a direct action of the venom on cardiomyocytes. We suggest that this direct effect on cardiac fibers may play a role in the development of cardiac arrhythmias and contractility defects following envenoming with T. serrulatus scorpion.

A histochemical study of catecholamines and cholinesterases in the autonomic nerves of the human minor salivary glands

SynopsisThe cholinergic and adrenergic innervation of human minor sublingual buccal and labial salivary glands has been studied with histochemical techniques for localizing acetylcholinesterase and catecholamines. A rich cholinergic innervation was observed around the acini, blood vessels and some ducts of the three glands.The adrenrgic innervation, however, was virtually absent from the parenchyma although present around the blood vessels, in marked contrast to the dense parenchymal adrenergic innervation observed in the human parotid and submandibular glands. These results suggest that the autonomic nervous mechanism which regulates salivary secretion is more elaborate in the major than in the minor salivary glands.

Depletion of radiosensitive leukocytes exacerbates the heart sympathetic denervation and parasitism in experimental Chagas' disease in rats

The acute phase of the Trypanosoma cruzi infection induces damage of the heart sympathetic nerve terminals in rats. The participation of the radiosensitive leukocytes in this process was assessed in young rats submitted to gamma irradiation 1 day before infection with T. cruzi, Y strain. Gamma irradiation increased the heart noradrenergic denervation evaluated at day 12 of infection by histochemical and electron-microscopic methods. The presence of numerous macrophages with ultrastructural features of activation and a significant rise in the myocardial parasitism suggest the involvement of radioresistant macrophages or parasite factors, or both, on the damage of the nerve terminals.

Cardiac NGF and GDNF expression during Trypanosoma cruzi infection in rats

In rats, autonomic nerve endings are damaged during Trypanosoma cruzi-induced myocarditis. Gradual recovery occurs after the acute phase. The present work shows the cardiac levels of glial cell line-derived neurotrophic factor (GDNF) and nerve growth factor (NGF), and their cellular sources during T. cruzi infection in rats. Atrial and ventricular NGF levels (ELISA) increased significantly at day 20 post inoculation, the time-point of maximal sympathetic denervation. ELISA failed to show significant increase of cardiac GDNF levels. However immunohistochemistry showed a significant increase of anti-GDNF gold particles over atrial granules at day 20. Light microscopy showed stronger NGF immunostaining in atrial cardiomyocytes and several blood capillaries. In situ hybridization showed NGF and GDNF mRNAs in atrial and ventricular myocytes of both infected and uninfected animals. Endothelial cells exhibited NGF mRNA and protein only in infected rats. No evidence of neurotrophic factor expression by the infiltrating mononuclear cells was found. This is the first report on neurotrophic factor expression during T. cruzi infection. Our findings indicate an important role for NGF in the regenerative phenomena subsequent to a myocarditis able to damage sympathetic nerve endings, with preservation of preterminals and nerve trunks. GDNF could have a minor or a more transient participation.

Noradrenergic and acetylcholinesterase-positive nerve fibres of the uterus in sexually immature and cycling rats

SummaryThe distribution and density of the noradrenergic and acetylcholinesterase-positive nerve fibres were histochemically studied in different uterine regions of prepubertal and cycling rats in dioestrus and oestrus. Besides the rich and double innervation of blood vessels, both types of nerve fibre were found in the myometrium and cervical musculature. The non-vascular noradrenergic network looked denser at the tubal end of the horns and at the cervix, whereas the acetylcholinesterase-positive innervation was poor at the tubal end, increasing toward the cervix. Contrasting with the middle third of the uterine horn, at the tubal end, the myometrial longitudinal layer was much more innervated than the circular one, especially by the noradrenergic nerve fibres. The prepubertal rats presented an adult pattern of uterine autonomic innervation. In the cycling animals, this innervation was nearly the same during oestrus and dioestrus regarding both the density of nerve fibres and intensity of the histochemical reactions.

Catecholamine-containing neurons in Schistosoma mansoni

SummaryFalcks method for the demonstration of monoamines was applied to the flatworm Schistosoma mansoni. Whole mount preparations and sections of frozen dried specimens showed that a primary catecholamine is present in four pairs of large nerve cells and in two longitudinal fiber tracts showing varicosities. Smaller neurons were found along these tracts. They are united by commissures and give off many branches which end in small dilatations.

Sympathetic Innervation of the Reproductive Organs of the Male Opossum, Didelphis albiventris (Lund, 1841)

The dissection of nerves and ganglia anatomically related to the pelvic organs revealed one inferior mesenteric ganglion, two testicular ganglia, two hypogastric nerves, two pelvic ganglia and two pelvic nerves. The histochemical demonstration of catecholamines by a glyoxylic acid fluorescence method revealed a rich sympathetic innervation in the ductus deferens, in the three segments of the prostate and in the convoluted ductuli efferentes. The testis, epididymis and all three pairs of bulbourethral glands presented fluorescent nerve fibers only around blood vessels. Removal of the inferior mesenteric and testicular ganglia, and hypogastric neurectomy with our without ligature and sectioning of testicular arteries, had no effect on the density of the nonvascular fluorescent fibers. Removal of the periprostatic tissue caused complete denervation of the prostate and marked denervation of the ductuli efferentes and ductus deferens. Small ganglia containing fluorescent nerve cell bodies were found close to the capsule of the prostate. The results indicate that short adrenergic neurons are responsible for the sympathetic innervation of the reproductive organs of the male opossum.

Mast cell types and cell-to-cell interactions in lymph nodes of the opossum Didelphis albiventris

Previous light-microscopic studies have shown a unique population of mast cells in lymphatic sinuses of lymph nodes located in the head, neck, axillary fossa and inguinal region of the opossum. In the present work, scanning and transmission electron-microscopic studies in the opossum mandibular and superficial axillary lymph nodes have strengthened the differences between connective-tissue mast cells (CTMC) and the lymphatic-sinus mast cells (LSMC). Further, close appositions of mast cells to other cells were described. At the nodal capsule, CTMC contacted fibroblast and granulocytes. In the lymphatic sinuses a few CTMC contacted LSMC, macrophages and reticular cells. The LSMC contacted macrophages, reticular cells and other LSMC. A few LSMC could be located in the medullary cord in close contact with plasma cells or other lymphoid cells, keeping the same ultrastructural features of those found in the lymphatic sinuses. An important new finding was provided by light-microscopic studies in nine abdominal lymph nodes. Most of them (para-aortic, common iliac, cardial, cecocolic and those of the body and tail of the pancreas) displayed numerous LSMC with the same distribution and histological features described herein. However, the mesenteric, pyloric and head-of-pancreas lymph nodes were virtually devoid of LSMC. Instead, their mast cells occurred mainly at the medullary cords and were very similar to the CTMC. Ultrastructural studies at the mesenteric lymph nodes confirmed the CTMC character of the mast cells located at both medullary cords and sinuses, and disclosed interactions with macrophages and lymphoid cells.

Monoamines in the C cells of the thyroid gland of callithricid primates

SummaryThe thyroid gland of three species of marmosets were studied with the Falck and Hillarp fluorescence technique for monoamines. Two types of fluorescent C cells were observed. The predominant type displayed the greenish (or blue) fluorescence characteristic of catecholamines. The other type displayed a yellowish fluorescence most probably due to 5-HT. The presence of monoamines in C cells now reported for the first time in Primates offers an interesting possibility for studying their presumed role in calcitonin secretion.