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Biomedical subjects

A B Machado

Publications and source records attributed to A B Machado.

At least 19 recordsLinked to original sources
PubMed2000

Sera from chronic chagasic patients depress cardiac electrogenesis and conduction.

We report results obtained with sera from 58 chronic chagasic patients that were evaluated for effects on heart rate and atrioventricular (AV) conduction in isolated rabbit hearts and screened for the presence of muscarinic and beta-adrenergic activity. We show that sera from 26 patients decreased heart rate, while 10 increased it and 22 had no effect. Additionally, sera from 20 of the 58 patients blocked AV conduction. Muscarinic activation seems to be involved in both effects, but is not the only mechanism, since atropine did not antagonize the decrease in heart rate in 23% of sera or AV block in 40%. Sera from patients with complex arrhythmias were significantly more effective in depressing both heart rate and AV conduction. Sera that induce increases in heart rate seem to operate exclusively through beta-adrenergic activation. Two of these sera, evaluated with respect to intercellular communication in primary cultures of embryonic cardiomyocytes were able to block gap junction conductance evaluated by a dye injection technique after 24-h exposure. The mechanisms underlying this uncoupling effect are currently being investigated.

Analysis of Variance↗
PubMed1998

A better way to measure disability in older people.

BACKGROUND: Health care experts, older people and carers were asked to weight 18 personal and social activities of daily living (ADLs) with regard to the importance of being able to perform them. RESULTS: All groups agreed on the order of importance but experts gave greater weight to personal ADLs. We have used these results to produce a ratio scale.

Activities of Daily Living↗
PubMed1998

Central nervous system metastases from breast carcinoma. A clinical and laboratorial study in 47 patients.

In this retrospective study, 47 patients with clinical diagnosis of central nervous system metastases of breast cancer were evaluated by computerized tomography (CT), magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) examination. The patients were divided in 2 groups: 1, without leptomeningeal neoplasm and 2, with leptomeningeal neoplasm. In the group 2, the time interval between the primary disease and the central nervous system metastasis as well as the survival time were shorter than in group 1 (40 and 4.3 months in group 2 versus 57 and 10 months respectively, in group 1). In both groups the most common neurological symptoms and signs were intracranial hypertension and motor deficits. The most sensitive diagnostic methods were CT and MRI in group 1, and the CSF examination in group 2. The use of the tumor markers CEA and CA-15.3 in the routine examination of CSF showed promising results, mainly in leptomeningeal forms.

Adult↗
PubMed1992

Autonomic innervation of the salivary glands in cebid monkeys: a histochemical study.

The autonomic innervation of the major and minor salivary glands was studied in five species of cebid monkeys using acetylcholinesterase (AChE) and catecholamine histochemistry. Catecholamine-containing and AChE-positive nerve fibres were observed in the vessels and secretory endpieces of all glands, with no apparent predominance of one type over the other. In the intralobular ducts, however, the cholinergic innervation predominates. In the major salivary and minor sublingual glands the density of the nervous supply was higher, whereas in the secondary mandibular and posterior lingual glands it was less dense. The morphological patterns of salivary gland innervation found in Cebidae are compared with those of the related family Callitrichidae.

Acetylcholinesterase↗
PubMed1990

The pineal recess of the opossum: a scanning and transmission electron microscope study.

Scanning and transmission electron microscope studies were performed in the pineal recess region of eighteen adult Didelphis albiventris opossums. With the scanning electron microscope, three concentric regions could be observed in the pineal recess: a central zone lined by cells free of cilia or microvilli, or by a meshwork of interdigitating cell processes; an intermediate zone lined by microvillous cells; and a peripheral zone, lined by ciliated cells. The transmission electron microscope revealed that the central zone is lined mainly by pinealocytes. The lining cells are frequently overlaid by a meshwork of pinealocytic and glial processes. A "subsurface labyrinth" (a meshwork of cellular processes underneath the lining cells) is constantly seen in the central zone. The intermediate zone is lined by elongated microvillous ependymal cells, and the peripheral zone by typical ependyma. The large liquor-contacting area in the pineal recess region, as well as the peculiar organization of its surface, suggest a complex interrelationship between the liquor and the pineal gland of the opossum.

Animals↗
PubMed1989

[Histologic study of the pineal organ in tinamid birds].

The pineal organs of 10 species of tinamid birds belonging to the genera Crypturellus, Nothura, Rhynchotus and Tinamus were studied in serial microscopic sections of the entire medial region of the brain. All were located in a triangular space formed by the cerebral hemispheres and the cerebellum. They have the form of a club with the enlarged distal part enclosed in the dura-mater. In all species the pineal is formed of tubulofollicular structures, the walls of which are covered by a pseudo-stratified epithelium with elongated cells. In Rhynchotus and Nothura there is a predominance of small follicles with a reduced lumen and a regular outline, whereas in Tinamus and Crypturellus there is a predominance of large follicles with a wide lumen and an irregular outline. Our results show that morphological organization of the pineal organs in tinamids is similar to that observed for the majority of modern birds, in spite of the fact that they are generally regarded as very primitive.

Animals↗
PubMed1988

Annulate lamellae in the pineal organ of a tinamid bird.

This study reports the occurrence of annulate lamellae in the rudimentary photoreceptor cells of the pineal organ of a tinamid bird Crypturellus parvirostris. The annulate lamellae observed in these cells are located in the cell body and are comprised of 1 to 8 parallel lamellae, symmetrically aligned and regularly spaced. Each lamella consists of pairs of parallel membranes interrupted by regularly spaced pores or annuli. These observations are discussed and compared with the structure and distribution of these organelles referred in the literature.

Animals↗
PubMed1987

Changes in choline acetyltransferase activity of rat tissues during Chagas' disease.

1. The activity of choline acetyltransferase (CAT) measured by a radiolabeling method was significantly reduced in the heart, submandibular gland and esophagus of rats 20 days after inoculation with Trypanosoma cruzi (Y strain). 2. Normal enzyme activity was recovered in all these organs 100 days after inoculation. 3. In the transverse colon, no change, 30% reduction and normal activity were found at days 20, 100 and 430 of infection, respectively. 4. The data indicate recovery of parasympathetic function in experimental Chagas' disease. Axonal regrowth and sprouting are discussed as possible candidates for the recovery mechanisms.

Animals↗
PubMed1984

Adrenergic innervation and noradrenaline content of the rat submandibular gland during the experimental Trypanosoma cruzi infection.

Rat submandibular glands were tested histochemically for the presence of formaldehyde induced fluorescence 18, 32, 45, 60 and 100 days after inoculation with Y strain of Trypanosoma cruzi. At days 32, 60 and 100 the glandular noradrenaline content was also assayed fluorometrically. The fluorescent varicose nerve fibres of all the studied glands were severely reduced at days 18 and 32 of infection. At day 45 reduction was not so pronounced and by day 60 the density of adrenergic terminals was similar to that of the control glands. At day 32 of infection the glandular contents of noradrenaline expressed as ug/gland or ug/g of fresh tissue dropped to 50% of the control values. At day 64, the noradrenaline contents per gland were still different from the controls. However, at day 100 no difference was observed between the values for control and infected animals. These results indicate that the sympathetic innervation of the rat submandibular gland is affected during the acute phase of Chagas' disease but returns to normality during the chronic phase.

Adrenergic Fibers↗
PubMed1984

Cardiac noradrenalin in relation to protein malnutrition in chronic experimental Chagas' disease in the rat.

Rats inoculated with Trypanosoma cruzi were divided into two groups maintained, respectively, on a low and a rich protein diet. Ninety-eight days after inoculation the cardiac levels of noradrenalin in the well-nourished infected rats were not different from those of uninfected controls. In the malnourished group, however, these levels were around 50% of the control values. In addition, the adrenergic nerve terminals were clearly reduced in the auricular appendages of 87.5% of the malnourished infected rats. These results indicate that protein deficiency at least delays the recovery of noradrenalin levels that normally occurs during the chronic phase of experimental Chagas' disease.

Adrenergic Fibers↗
PubMed1981

Autonomic innervation of salivary glands in the armadillo, anteater, and sloth (Edentata).

The intraglandular distribution of adrenergic and cholinergic nerve fibers was studied histochemically in the parotid, mandibular, and sublingual glands of six species of edentates belonging to the three families that comprise the order; namely the Dasypodidae (armadillos), the Myrmecophagidae (anteaters), and the Bradipodidae (sloths). The following histochemical techniques were used: (a) acetylcholinesterase reaction for the demonstration of cholinergic fibers; (b) formaldehyde- and glyoxylic acid-induced fluorescence for the demonstration of adrenergic fibers. In addition, norepinephrine (NE) was assayed fluorimetrically in the mandibular and parotid glands of the armadillo. A network of acetylcholinesterase-positive nerve fibers surrounds the intra- and interlobular ducts and endpieces of all glands; it is of low density in the mandibular and sublingual gland of the sloth, of high density in the sublingual gland of the anteater and of moderate density in the remaining glands. A vascular cholinergic innervation occurs in all salivary glands. Although present around the vessels, adrenergic new fibers were virtually absent from the parenchyma of all glands, even after in vitro incubation of glandular tissue with NE or after administration of NE to armadillos previously treated with a monoamine oxidase (MAO) inhibitor. Consistent with this fact, the amount of NE present in the parotid and mandibular gland of the armadillo was extremely low. These findings may indicate that the salivary secretion in the edentates is regulated by the parasympathetic rather than by the sympathetic nervous system.

Adrenergic Fibers↗
PubMed1979

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

The 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 adrenergic 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.

Acetylcholinesterase↗
PubMed1978

Recovery from heart norepinephrine depletion in experimental Chagas' disease.

Norepinephrine (NE) was assayed fluorimetrically in the hearts of rats killed at different periods after inoculation with the Y strain of Trypanosoma cruzi. The levels of cardiac NE which, as reported previously, were not measurable 18, 22, and 32 days after inoculation became detectable at day 48. At day 70 these levels were around 50% of the control values and at day 97 normal values were attained in most animals. These results strongly suggest that sympathetic nerve fibers are destroyed in the acute phase of T. cruzi infection and regenerated during the chronic phase.

Animals↗