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Biomedical subjects

M Marques

Publications and source records attributed to M Marques.

At least 37 records · Page 2Linked to original sources
PubMed1991

Immunohistochemical localization of insulin-like materials in antral gastric mucosa and intestinal epithelial cells of the turtles Chrysemys dorbigni and Phrynops hilarii.

Immunoreactive insulin was demonstrated immunohistochemically with antibodies to human and porcine insulin by the avidin-biotin-peroxidase complex method in open-type gastrointestinal cells from sections of the antral stomach and of the upper, middle and lower intestine of the turtles Chrysemys dorbigni and Phrynops hilarii. In both species the concentration of cells positive for insulin-like material was higher in the gastric antrum than in the gut. The localization of insulin-like material in gastrointestinal mucosal cells of turtles is an unusual finding among vertebrates, because the insulin-containing cells migrate from the mucosal epithelium of the intestine early in vertebrate evolution to the acinar pancreas. The chemical nature of the gastrointestinal insulin-like material and its physiological role remain to be determined.

Animals↗
PubMed1989

Glycemia and immunohistochemical changes in the endocrine pancreas of the turtle Chrysemys dorbigni treated with streptozotocin.

The diabetogenic action of streptozotocin (SZ) was investigated in the turtle Chrysemys dorbigni after a 1- or 14-day fast. SZ (130 or 250 mg/kg) was injected intravenously, and blood glucose and plasma insulin were measured. Pancreatic endocrine cells were stained immunohistochemically by the immunoperoxidase avidin-biotin-peroxidase complex method. Only 14% of the SZ-treated turtles showed hyperglycemia. Prolonged fasting did not increase the percentage of hyperglycemic animals. In control turtles, insulin (beta)-, glucagon (alpha)- and somatostatin (delta)-immunoreactive cells were detected in increasing order of frequency. The qualitative changes seen in cells from the hyperglycemic SZ-treated turtles were more evident in beta and delta cells.

Animals↗
PubMed1989

High-dose intravenous immunoglobulin modifies complement-mediated in vivo clearance.

The mechanism of effect of high-dose intravenous immunoglobulin (IVIG) therapy in immune cytopenias is incompletely known. One of the leading theories ascribes the short-term effects of IVIG to the competition of infused IVIG for Fc receptors, thereby inhibiting IgG-mediated clearance. Using a system independent of IgG-Fc receptor interactions, we examined another potential mechanism of IVIG action. Guinea pigs were infused with a human IVIG preparation at 600 mg/kg/day for two consecutive days. Parallel groups of animals were treated with the same volume and/or concentration of saline and albumin. Clearance of IgM-sensitized guinea pig erythrocytes, which is wholly complement dependent, was significantly retarded in animals treated with high-dose IVIG. The effect was specific for IVIG, since human albumin (as a second foreign protein) failed to change the clearance of IgM-sensitized guinea pig erythrocytes. Experiments in which IVIG-treated animals were subjected to pre- and posttreatment clearance studies revealed heterogeneity among individual animals in respect to their response to IVIG infusions. Decrease of available plasma complement components did not account for the effect, since both C3 and CH50 values remained unchanged after IVIG treatment, despite rising levels of IVIG in sera of treated animals. The results of in vitro C3 uptake studies and the effect of IVIG on clearance of preopsonized cells suggest that IVIG produces a kinetic depression of C3 uptake and modifies the process of complement fragment deposition on erythrocytes. A generalized effect on mononuclear phagocytes is less likely but cannot be wholly ruled out. These studies establish another potential mechanism of IVIG action and suggest extension of its use to other complement-mediated diseases.

Animals↗
PubMed1987

A technique for collecting cerebrospinal fluid using an intraventricular cannula in rats.

The difficulty in obtaining cerebrospinal fluid (CFS) in an efficient and simple manner in rats prompts us to introduce a new technique that makes use of a cannula placed in the lateral ventricle. The cannula is implanted with a stereotaxic apparatus and the CSF is collected with a glass capillary tube. The technique has proved to work well for experiments in which the CSF must be free of blood. It also permits the collection of volumes of CSF sufficient for radioimmunoassays, and may be used in chronic experiments.

Animals↗
PubMed1986

Characterization of the insulin-binding sites in turtle thyroid microsomes.

The characteristics of the specific binding of labelled insulin to turtle thyroid microsomes were investigated. Binding experiments were performed in Krebs-Ringer bicarbonate buffer (pH 7.4) at 25 or 4 degrees C for different periods of time. Dissociation of the labelled insulin from the binding sites was also evaluated. It was found that the binding is dependent on time, temperature and microsomal protein concentration, with an optimum pH of 8.0. Unlabelled insulin and pro-insulin competed with the labelled insulin, binding in direct proportion to their biological activities, while glucagon and growth hormones did not compete for the binding sites. Scatchard plot analysis established the presence of binding sites of high and low affinities, and the rate of dissociation of bound insulin was considerably increased by the addition of unlabelled insulin. Both results are compatible with a negative co-operativity site-site interaction model. Trypsin abolished the insulin binding. These findings indicate that the microsomes from the turtle thyroid gland contain specific binding sites for insulin. However, pre-incubation of microsomes with phospholipase C or S-adenosyl-L-methionine (SAM), or incubation in the presence of 2 mol NaCl/l did not increase the specific insulin binding. Therefore, the binding properties are similar to those observed in mammalian insulin-responsive tissues except for the absence of the effects of 2 mol NaCl/l, phospholipase C or SAM, which suggests the absence of masked insulin-binding sites.

Animals↗
PubMed1985

Specific uptake, dissociation, and degradation of 125I-labeled insulin in isolated turtle (Chrysemys dorbigni) thyroid glands.

Thyroid glands from turtles (Chrysemys dorbigni) pretreated with potassium iodide were incubated with 125I-insulin in the presence or absence of unlabeled insulin, in order to study its specific uptake. At 24 degrees, the specific uptake reached a plateau at 180 min of incubation. The dose of bovine insulin that inhibited 50% of the 125I-insulin uptake was 2 micrograms/ml of incubation medium. Most of the radioactive material (71%) extracted from the gland, after 30 min incubation with 125I-insulin, eluted in the same position as labeled insulin on Sephadex G-50. Only 24% eluted in the salt position. After 240 min incubation, increased amount of radioactivity appeared in the Na125I position. When bovine insulin was added together with the labeled hormone, a substantial reduction of radioactivity was observed in the insulin and Na125I elution positions. Dissociation studies were performed at 6 degrees in glands preincubated with 125I-insulin either at 24 or 6 degrees. The percentage of trichloroacetic acid (TCA)-soluble radioactive material in the dissociation medium increased with incubation time at both temperatures. However, the degradation activity was lower at 6 than at 24 degrees. The addition of bovine insulin to the incubation buffer containing 125I-insulin reduced the radioactive degradation products in the dissociated medium. Chloroquine or bacitracin inhibited the degradation activity. Incubation of thyroid glands with 125I-hGH or 125I-BSA showed values of uptake, dissociation, and degradation similar to those experiments in which an excess of bovine insulin was added together with the labeled hormone. Thus, by multiple criteria, such as specific uptake, dissociation, and degradation, the presence of insulin-binding sites in the turtle thyroid gland may be suggested.

Animals↗
PubMed1985

Effects of thyroid hormones on the hippocampal glial cells of fasting rats.

The effects of the oral administration of thyroid hormones on the hippocampal glial cells in fasting or fed adult rats were studied. The hormone treatment and/or fasting were done during two periods of five days interpolated by ten days without any hormone treatment or fasting. Prominent histological changes and increased number of glial cells were observed in the hippocampus of rats when the thyroid hormone administration was associated with fasting.

Animals↗
PubMed1984

Insulin binding sites and action in the adrenal glands from normal and streptozotocin diabetic rats.

Insulin binding to rat adrenal glands was studied in vivo by i.v. injection of 125I-insulin either alone or together with an excess of unlabelled hormones (insulin, glucagon, prolactin, or growth hormone). In addition, isolated glands from normal or streptozotocin diabetic rats (STZ) were incubated in vitro with 125I-insulin and varying concentrations of unlabelled insulin. Both experiments showed specific binding sites in the adrenal glands. Furthermore the glands from diabetic rats bound more insulin than the glands from controls. The insulin stimulatory effect on the deoxyglucose (14C-DG) uptake was examined in isolated glands from normal and STZ rats. Adrenal glands from control rats exhibited higher basal values of 14C-DG uptake than glands from STZ rats. Insulin induced a stimulatory effect on the 14C-DG transport in glands from both control and diabetic rats. Adrenal glands from STZ rats responded much earlier to exogenous insulin, however the maximal stimulating concentration of the hormone did not restore the 14C-DG uptake to control values. The lowest concentration of insulin that increased the 14C-DG transport was 3 X 10(-8) M. The adrenal gland must be considered a target organ for insulin by both criteria, insulin specific binding and stimulatory action on the deoxyglucose transport.

Adrenal Glands↗
PubMed1984

In vivo specific uptake of labeled insulin by turtle (Chrysemys dorbigni) thyroid gland.

Insulin labeled with 125I was injected into turtles to study its specific uptake by the thyroid gland. The gel filtration behavior of labeled material in blood and thyroid gland was determined in order to ascertain if the uptake is specific. Most animals were pretreated with KI to saturate the gland with iodide. Maximum specific uptake of radioactivity by the thyroid gland was only detected in animals pretreated with KI. A significant dose-related reduction (ED50 = 0.5 micrograms/kg) was observed when unlabeled insulin was administered simultaneously with 125I-insulin. Prolactin, glucagon and growth hormone (2 mg/kg) did not affect 125I-insulin uptake. Most of the radioactive material extracted from the turtle thyroid 15 min after 125I-insulin injection coeluted with 125I-insulin on Sephadex G-50. This peak decreased as a function of time after 125I-insulin administration. Similar elution patterns were found for thyroid extracts from turtles previously treated with KI. The labeled hormone in the gland was rapidly degraded or processed to both higher and lower molecular weight compounds. Prior administration of KI suppressed the former, whereas when unlabeled insulin was injected simultaneously with 125I-insulin the amount of degradation products was reduced. The demonstration of radioactive degradation products is consistent with the intracellular receptor-mediated degradation hypothesis. These findings indicate the presence of specific insulin-binding sites in the thyroid gland.

Animals↗
PubMed1984

Sex differences of normal dogs in lipid mobilization and blood glucose levels after glucose or insulin infusion.

The influence of sex hormones on carbohydrate and lipid homeostasis was studied by comparing the response to glucose or insulin infusion in male and female dogs. The levels of blood glucose, serum immunoreactive insulin (IRI) and plasma free fatty acids (FFA) were determined. The hyperglycemia induced by glucose infusion (10 mg min-1 kg-1) for 60 min in summer was significantly higher in male than in female dogs. This sex difference in the response was confirmed in experiments performed in winter, when blood glucose levels of both sexes in response to the infusion reached higher values than those found in summer. The increase of serum IRI in response to glucose infusion was similar in both sexes in the summer experiment, while in winter the increase was significantly reduced and delayed in males. Glucose infusion into male and female dogs induced no significant changes in plasma FFA concentration in experiments carried out in winter or summer. Insulin infusion (16.6 mU min-1 kg-1) caused hypoglycemia in both sexes, which was of earlier onset in the females. The antilipolytic effect of insulin occurred in both sexes and was also stronger in females. The data show sexual and seasonal differences in response by dogs to glucose infusion and emphasize the participation of sex hormones in the homeostasis of energy substrates.

Animals↗
PubMed1980

ABO aggulutinins from Biomphalari straminea snails.

Extracts from B. straminea spawn are active against A and B normal red cells. A1 and A2 subgroups may be differentiated with trypsin-, papain- and pronase-treated cells. 0 cells treated with papain, pronase and neuraminidase react weakly to the extracts.

ABO Blood-Group System↗
PubMed1980

Agglutinins and hemolysins from Biomphalaria tenagophila snails.

A saline anti-A and incomplete anti-A,B agglutinin were found in spawn extracts of Biomphalaria tenagophila snails. Significance differences after papain and pronase treatments were also found for A1 and A2 subgroups. The hemolysin titers are high, and unspecific.

ABO Blood-Group System↗