Biomedical subjects

C R Machado

Publications and source records attributed to C R Machado.

At least 37 records · Page 2Linked to original sources

PubMed1996

Rates of lipid metabolism in adipose tissue of pigs adapt to lactational state and dietary energy restriction.

To define better the role of metabolism in adipose tissue during gestation and lactation, adaptations to gestation, lactation and to decreased energy intakes were determined using pigs as a model. The effects of energy restriction and the interactions of restriction during both periods were tested by feeding one of two rations during gestation to provide either 19.3 or 25.1 MJ of metabolizable energy per day (ME/d) and adequate amino acids, vitamins and minerals. Pigs from each gestation treatment then consumed 27.7, 48.6, or 69.0 MJ of ME/d during lactation. Body weight and subcutaneous fat thickness were lower in the energy-restricted groups. Litter growth was slower only in the group receiving the lowest energy in gestation and lactation. During gestation, fatty acid synthesis, as measured in in vitro tissue incubations, was lower in subcutaneous adipose tissue of pigs consuming 19.3 compared with 25.1 MJ of ME/d. In pigs fed the highest energy, rates of lipogenesis and esterification were faster after parturition. Feeding 48.6 or 27.7 MJ of ME/d reduced lipogenesis during lactation by approximately 75 and 90% and rates of esterification by 35 and 60%, respectively, compared with controls fed 69.0 MJ of ME/d. Rates of lipid synthesis at d 7 of lactation were higher than at d 23. Lipolysis was approximately twofold higher due to energy restriction. Lactation alone did not alter lipolysis compared with during gestation. The first-committed step of glucose conversion to fatty acids was decreased in a manner sensitive to energy restriction. Recycling of fatty acids was maintained at a significant rate regardless of energy intake. Lipid metabolism in adipose tissue of pigs during lactation is regulated in a manner similar to that observed in humans.

Adaptation, Physiological↗

PubMed1994

Trypanosoma cruzi infection in rats induced early lesion of the heart noradrenergic nerve terminals by a complement-independent mechanism.

The acute phase of the experimental Chagas' disease in rats induces extensive lesion of the heart sympathetic nerve terminals. Because of evidence indicating the involvement of immune reactions in neuron destruction provoked by Chagas' disease, we tested the effects of depleting the complement system by cobra venom factor upon the sympathetic denervation. The serum hemolytic activity against sensitized sheep erythrocytes ensured the efficacy of the anticomplementary treatment. Glyoxylic acid-induced histofluorescence and electron-microscopic methods allowed the study of the heart noradrenergic nerves. T. cruzi infection caused marked rarefaction of fluorescent nerve terminals at day 10 of infection and the ultrastructural study guaranteed that this rarefaction involved lesion of noradrenergic terminals. The complement depletion failed to prevent this early heart noradrenergic denervation, excluding the participation of complement-mediated lysis as a main mechanism.

Animals↗

PubMed1994

Histochemical and ultrastructural studies of mast cells in the intestinal mucosa and skin of the opossum Didelphis albiventris.

The mast cells located in the intestinal mucosa of a non-eutherian mammal were studied in comparison with those in the skin of the ear. In the intestinal mucosa, the mast cells exhibited a more variable shape, larger cytoplasmic granules and greater sensitivity to fixatives regarding their staining towards Toluidine Blue. Ultrastructurally, these granules were more heterogeneous but lacked the crystalline content found in granules of skin mast cells; lipid body-like organelles were found only in the mucosa-located mast cells. Histochemically, they differed from skin mast cells by the absence of periodic acid-Schiff (PAS)-positive granules. Unlike the mucosal mast cells of the rat, they fluoresced brilliant yellow after berberine treatment, which is evidence of the presence of heparin.

Animals↗

PubMed1993

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

The 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.

Acetylcholinesterase↗

PubMed1992

Mast cell types in the lymph nodes of the opossum Didelphis albiventris (Marsupialia, Didelphidae).

Using histological and histochemical techniques, we have found a unique population of mast cells in the lymphatic sinuses of lymph nodes from different anatomical regions of the opossum. The lymphatic-sinus mast cells of the medullary sinuses were numerous, and could be easily distinguished from the connective-tissue mast cells of the dermis and lymph node capsule by their larger size and their enlarged cytoplasmic granules that were also more heterogeneous in shape and staining properties.

Animals↗

PubMed1992

Control of adipose tissue lipolysis in ectotherm vertebrates.

Lipolytic activity of fish (Hoplias malabaricus), toad (Bufo paracnemis), and snake (Philodryas patagoniensis) adipose tissue was investigated in vivo and in vitro. Catecholamines or glucagon did not affect the release of free fatty acids (FFA) by incubated fish and toad adipose tissue. Catecholamines also failed to activate snake adipose tissue lipolysis, which even decreased in the presence of epinephrine. However, glucagon stimulated both the lipolytic activity of reptilian tissue in vitro and the mobilization of FFA to plasma when administered to snakes in vivo. The release of FFA from incubated fish, amphibian, and reptilian adipose tissue increased markedly in the presence of cAMP or xanthine derivatives, inhibitors of phosphodiesterase. Forskolin or fluoride, activators of specific components of the adenylate cyclase system, strongly stimulated toad adipose tissue lipolysis. The data suggest that adipocyte triacylglycerol lipase of ectotherm vertebrates is activated by a cAMP-mediated phosphorylation and that the organization of the membrane-bound adenylate cyclase system is similar to that of mammals.

Adenylyl Cyclases↗

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

Rat adrenal gland in experimental American trypanosomiasis: immunocytochemical study of tissue parasitism.

The rat adrenal gland is poorly parasitized during the experimental infection with Y strain of Trypanosoma cruzi. In both cortical and medullary regions, the parasitism peaked at day 10 and was characterized by the predominance of single amastigotes over nests containing 2 or more parasites. After day 10 of infection, the tissue parasitism dropped rapidly to become practically null at day 32 of infection. In cortical tissue, the amastigotes occurred mainly inside the endocrine cells. In the medulla, they found mainly in glial cells and non-identified stromal cells. In both cortex and medulla, inflammatory processes were found till day 20 of infection. Our data do not support the hypothesis that a corticoid rich environment would favor T. cruzi parasitism in adrenal medulla.

Adrenal Cortex↗

PubMed1989

Effect of fasting on glucose turnover in a carnivorous fish (Hoplias sp).

Intravenous glucose tolerance tests and measurements with [6-3H]glucose of rate of glucose replacement, transit time, and body glucose mass were performed in fed and fasted Hoplias malabaricus. Both glycemia levels and the rate of decline of blood glucose following intravenous administration of 500 mg/kg glucose were significantly lower in 60-day-fasted than in fed fish. Changes in plasma free fatty acids were opposite to those in blood glucose. The rate of glucose replacement, calculated graphically from mean +/- 3 SE plots of glucose specific radioactivity, was 0.71 (0.66-0.77) mg.kg-1.min-1 in fed H. malabaricus and decreased to 0.51 (0.46-0.56) mg.kg-1.min-1 after 60 days without food, with a concomitant reduction of body glucose mass (mmin, 138 vs. 83 mg/kg). In fish starved for 10 mo the rate of glucose replacement and body glucose mass were further reduced to 0.35 (0.29-0.42) mg.kg-1.min-1 and 57 mg/kg (mmin), respectively. It is concluded that a progressive decline in the rate of glucose utilization contributes to the adaptation of fish to prolonged fasting.

Animals↗

PubMed1989

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.

Animals↗

PubMed1988

Effects of starvation, refeeding, and insulin on energy-linked metabolic processes in catfish (Rhamdia hilarii) adapted to a carbohydrate-rich diet.

The effects of starvation and of a short period of refeeding on energy-linked metabolic processes, as well as the effects of insulin administration, were investigated in an omnivorous fish (catfish, Rhamdia hilarii) previously adapted to a carbohydrate-rich diet. Following food deprivation blood sugar levels declined progressively to about 50% of fed values after 30 days. During the same period plasma free fatty acid (FFA) concentration increased twofold. Starvation resulted in reduced concentrations of lipid and glycogen in the liver and of glycogen, lipid, and protein in white muscle. However, taking into account the initial and final concentrations of tissue constituents, the liver weight, and the large fractions of body weight represented by muscle, it could be estimated that most of the energy utilized during starvation derived from the catabolism of muscle lipid and protein. Refeeding starved fishes for 48 hr induced several-fold increases in the rates of in vivo and in vitro incorporation of [14C]glucose into liver and muscle lipid and of [14C]glycine into liver and muscle protein. Incorporation of [14C]glucose into liver glycogen was also increased. However; refeeding did not affect the incorporation of labeled glucose into muscle glycogen, neither in vivo nor in vitro. Administration of pharmacological doses of insulin to normally fed catfishes resulted in marked increases in the in vivo incorporation of 14C from glucose into lipid and protein in both liver and muscle. In contrast, labeled glucose incorporation into muscle glycogen was not affected by insulin and label incorporation into liver glycogen was actually lower than that in noninjected controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1988

Morphometric and histological analysis of the superior cervical ganglion in experimental Chagas' disease in rats.

Histological methods were used for studying the left superior cervical ganglia of control and T. cruzi infected female rats killed 13, 20, and 34 days after inoculation. Concomitantly, the sympathetic innervation of the heart auricular appendages and of the submandibular gland was studied by a glyoxylic acid-induced fluorescence method for catecholamines. At day 34 of infection, the superior cervical ganglia of an additional group of control and infected animals were studied morphometrically through the determination of ganglion volume, total number, and nuclear diameter of the principal neurons. No amastigote pseudocyst could be detected inside the ganglia at any time during infection. Inflammatory reactions were very discrete or absent at day 13 of infection, but were clearly present at day 20 as periganglionitis (in all infected animals) or ganglionitis (in 62.5% of the infected animals). These reactions again became very discrete at day 34 of infection. None of the morphometric parameters analyzed were altered by Chagas' disease. Histochemical studies on the sympathetic innervation of the heart and submandibular gland showed disappearance or rarefaction of fluorescent nerve fibers, starting around the 13th day of infection. The involvement of sympathetic nerve terminals in Chagas' disease is a local phenomenon rather than a consequence of parasitism or destruction.

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↗

PubMed1986

Effect of adrenoceptor blockers on the acinar enlargement induced by Chagas' disease in the rat submandibular glands.

Chagas' disease induces acinar enlargement in the submandibular salivary gland of rats inoculated with the Y strain of Trypanosoma cruzi at the age of 27-28 days and killed 18 days after inoculation (acute phase). Propranolol, a beta-adrenoceptor blocker, prevents the acinar enlargement induced by T. cruzi infection. Phenoxybenzamine, an alpha-adrenoceptor blocker, enhances this enlargement. These results suggest that catecholamines are involved in the genesis of the acinar hypertrophy induced by Chagas' disease.

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

Changes in acetylcholinesterase-positive nerves of the submandibular salivary gland during experimental infection with a protozoon, Trypanosoma cruzi, in rats.

Using a thiocholine acetylcholinesterase histochemical technique, an appreciable reduction of the innervation was demonstrated in the submandibular glands of rats inoculated with the Y strain of Trypanosoma cruzi, at the early chronic phase of the infection. During the chronic phase of the disease there was recovery of the normal pattern of innervation in all infected animals.

Acetylcholinesterase↗

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↗

PubMed1982

Morphological and physiological factors involved in the contractility of the spermatic cord and ductus deferens of the opossum (Didelphis albiventris).

The opossum spermatic cord is characterized by a thick skeletal muscle coat, provided by the great development of the cremasteric muscle. Acetylcholine induced a powerful contraction of the spermatic cord placed in an organ bath containing Heller's solution. This contraction was blocked by curare but not completely by atropine as is usual for skeletal muscle. However, the ductus deferens did not respond to acetylcholine or catecholamines under the same conditions. Specific histochemical methods for both catecholamines and acetylcholinesterases revealed that the ductus deferens musculature, composed mainly of circular fibres, is richly innervated by adrenergic and presumed cholinergic nerve fibres. The lack of responsiveness to the neurotransmitters could be explained by the absence of longitudinally arranged muscle. It is suggested that in the opossum the cremaster could participate in the mechanism of sperm transport.

Acetylcholine↗