Search PubMed⌕ Search

Biomedical subjects

M C Oliveira

Publications and source records attributed to M C Oliveira.

At least 37 records · Page 2Linked to original sources
PubMed1999

Chronic effect of antidopaminergic drugs or estrogen on male wistar rat lactotrophs and somatotrophs.

The aim of the present study was to evaluate the effect of antidopaminergic agents on the somatotrophs in the presence of hyperprolactinemia. Adult male Wistar rats were divided into 6 groups: a control group and five groups chronically treated (60 days) with haloperidol, fluphenazine, sulpiride, metoclopramide or estrogen. Somatotrophs and lactotrophs were identified by immunohistochemistry and the data are reported as percent of total anterior pituitary cells counted. The drugs significantly increased the percentage of lactotrophs: control (mean +/- SD) 21.3 +/- 4.4, haloperidol 27.8 +/- 2.2, fluphenazine 34.5 +/- 3.6, sulpiride 32.7 +/- 3.5, metoclopramide 33.4 +/- 5.5 and estrogen 42.4 +/- 2.8. A significant reduction in somatotrophs was observed in animals treated with haloperidol (23.1 +/- 3.0), fluphenazine (22.1 +/- 1.1) and metoclopramide (24.2 +/- 3.0) compared to control (27.3 +/- 3.8), whereas no difference was observed in the groups treated with sulpiride (25.0 +/- 2.2) and estrogen (27.1 +/- 2.8). In the groups in which a reduction occurred, this may have simply been due to dilution, secondary to lactotroph hyperplasia. In view of the duplication of the percentage of prolactin-secreting cells, when estrogen was applied, the absence of a reduction in the percent of somatotrophs suggests a replication effect on this cell population. These data provide additional information about the direct or indirect effect of drugs which, in addition to interfering with the dopaminergic system, may act on other pituitary cells as well as on the lactotrophs.

Animals↗
PubMed1998

Simultaneous localization of Pit-1 protein and gonadotropins on the same cell type in the anterior pituitary glands of the rat.

Pit-1 is a prototypic member of the POU transcription factor family and plays a critical role in pituitary-specific action of growth hormone (GH), prolactin (PRL), and thyroid-stimulating hormone (TSH) beta-subunit genes. The purpose of the present study was to elucidate the changes in the expression of the Pit-1 product in the pituitary of pregnant rats employing an improved double-immunohistochemical method. The positive cells showed nuclear immunoreactivity and Pit-1 protein was frequently observed in the nuclei of many cells which were also immunopositive for GH, PRL, and betaTSH. Unexpectedly, a significant number of pituitary cells containing both Pit-1 and gonadotropins were also observed. These cells were usually distributed near blood vessels that supply the pituitary. While a prominent increase in the percentage of Pit-1/PRL, Pit-1/beta-luteinizing hormone and Pit-1/beta-follicle-stimulating hormone immunoreactive cells was observed in pregnant rats, the percentage of Pit-1/GH immunoreactive cells was strongly decreased. In contrast, no significant differences in the percentage of Pit-1/betaTSH doubly immunolabeled cells were noticed. Our findings strongly support the hypothesis that PRL could coexist in the Pit-1 immunopositive gonadotropes. Although Pit-1 protein was not detected in the nuclei of corticotropes, the existence of these cells in the rat pituitary cannot be excluded.

Animals↗
PubMed1997

Effects of bromocriptine on serum prolactin levels, pituitary weight and immunoreactive prolactin cells in estradiol-treated ovariectomized rats: an experimental model of estrogen-dependent hyperprolactinemia.

The present study was designed to assess the effects of bromocriptine, a dopamine agonist, on pituitary wet weight, number of immunoreactive prolactin cells and serum prolactin concentrations in estradiol-treated rats. Ovariectomized Wistar rats were injected subcutaneously with sunflower oil vehicle or estradiol valerate (50 or 300 micrograms/rat(-1) week (-1) for 2, 4, or 10 weeks. Bromocriptine (0.2 or 0.6 mg rat (-1) day (-1)) was injected daily during the last 5 or 12 days of estrogen treatment. Data were compared with those obtained for intact control rats. Administration of both doses of estrogen increased serum prolactin levels. No difference in the number of prolactin cells in rats treated with 50 micrograms estradiol valerate was observed compared to intact adult animals. In contrast, rats treated with 300 micrograms estradiol valerate showed a significant increase in the number of prolactin cells (P < 0.05). Therefore, the increase inn serum prolactin levels observed in rats treated with 50 micrograms estradiol valerate, in the absence of morphological changes in the pituitary cells, suggests a "functional" estrogen-induced hyperprolactinemia. Bromocriptine decreased prolactin levels in all estrogen-treated rats. The administration of this drug to rats previously treated with 300 micrograms estradiol valerate also resulted in a significant decrease in pituitary weight and number of prolactin cells when compared to the group treated with estradiol alone. The general antiprolactinemic and antiproliferative pituitary effects of bromocriptine treatment reported here validate the experimental model of estrogen-induced hyperprolactinemic rats.

Animals↗
PubMed1996

Effects of tamoxifen on serum prolactin levels, pituitary immunoreactive prolactin cells and uterine growth in estradiol-treated ovariectomized rats.

Pituitary effects of the antiestrogen tamoxifen are not well established, although estrogen is known to have a stimulatory role in prolactin secretion. Effects of tamoxifen on serum prolactin levels, pituitary wet weight and number of prolactin cells were studied. Ovariectomized female Wistar rats were injected, subcutaneously, with estradiol valerate, 50 or 300 micrograms/rat per week for 2 or 10 weeks. Tamoxifen was injected during the last days of estrogen treatment. Data were compared with two other groups, treated with estradiol valerate alone or estradiol valerate plus the dopamine agonist bromocriptine. Serum prolactin levels were increased by estrogen treatment with all doses used. Furthermore, rats treated with 300 micrograms of estradiol valerate, for 2 and 10 weeks, showed a clear increase in pituitary weight and number of prolactin cells (p < 0.05). Bromocriptine decreased prolactin levels, pituitary weight and the number of prolactin cells (p < 0.05). Tamoxifen associated to subacute period of estrogen administration resulted in a significant reduction of serum prolactin levels and pituitary weight (p < 0.05). No effects on prolactin levels or number of prolatin cells were observed with tamoxifen associated to chronic estrogen treatment. Tamoxifen also presented a dose-related inhibitory effect upon estrogen-stimulated rises in uterine weight and DNA content. In conclusion, the results of the present paper showed that tamoxifen reduced estrogen-stimulated prolactin levels in some, but not in other hormonal conditions and that these effects were not mediated by an inhibition of lactotroph cell growth. Further studies are needed to define the exact role of antiestrogens at molecular level in hyperprolactinemic states and their eventual connection with dopamine and its agonists.

Animals↗
PubMed1996

The effect of light on the biosynthesis of beta-carotene and superoxide dismutase activity in the photosynthetic alga Gonyaulax polyedra.

Daily oscillations of both beta-carotene and superoxide dismutase (SOD) activity are related to the intracellular control of reactive oxygen species (ROS). It is well established that ROS are present in all aerobic cells. We studied the marine dinoflagellate Gonyaulax polyedra which has been extensively used as a model to understand the biological clock at the molecular level. beta-Carotene, besides suppressing singlet molecular oxygen (1O2), may act as a photoreceptor pigment in many photosynthetic cells. The levels of beta-carotene during the day phase were shown to be twice as high as during the night phase. The dose-response curve for light-induced carotenoid synthesis was linear for up to 45 min of light exposure, after which night phase cells contained the same levels of beta-carotene as day phase cells. Cells exposed to light pulses at different times during the dark period displayed the highest beta-carotene induction in the middle of the night. SOD activity of cell-free extracts of G. polyedra was three to four times higher during the day. This rhythm continued in cells kept in constant light, indicating that the regulation can be attributed to the cellular circadian clock. No-denaturing polyacrylamide gels revealed the presence of several SOD isoenzymes in G. polyedra, including CuZnSOD and MnSOD. Furthermore, G. polyedra SOD cross-reacts with a polyclonal antibody raised against SOD. In addition to being gene regulated by ROS concentration, G. polyedra SOD expression seems also to be under the control of the biological clock.

Animals↗
PubMed1996

Effect of estrogen and neuroleptics on prolactin secretion and immunoreactive prolactin cells.

The use of estrogen and dopamine receptor antagonists is associated with elevated prolactin levels and, in rats, chronic estrogen treatment is also associated with lactotroph proliferation. In this study, haloperidol, fluphenazine, sulpiride and metoclopramide, alone or combined with estradiol, were administered to Wistar rats. Pituitary weight, serum prolactin levels and percent of immunoreactive prolactin cells in the anterior pituitary glands were determined at the end of 60 days of treatment. The pituitary weight of rats treated with estrogen alone or in combination with other drugs was significantly higher than the control group. The serum prolactin level was higher than the upper confidence limit in all but three of the 90 treated rats. While in the control group the percent of immunoreactive prolactin cells was 20%, administration of the neuroleptic drugs and metoclopramide increased this percent to approximately 30%, and estrogen alone or in combination with one of the neuroleptic drugs increased it to approximately 40%. The results presented here demonstrate the relationship between prolactin secretion and prolactin cell number when different neuroleptics and related drugs are used.

Animals↗
PubMed1995

Characterization of an exocellular serine-thiol proteinase activity in Paracoccidioides brasiliensis.

An exocellular proteinase activity has been characterized in Paracoccidioides brasiliensis culture filtrates. Chromatographic analysis showed that the activity was eluted from an anion-exchange Resource Q column at 0.08-0.1 M NaCl, and by gel filtration near ovalbumin elution, in a single peak. Purification of the proteinase, however, was hampered by the low protein yield, in contrast to the high peptidase activity. Numerous chromogenic peptidyl p-nitroanilide derivatives and internally quenched fluorescent peptides, flanked by Abz (O-aminobenzoyl) and EDDnp (ethylenediaminedinitrophenyl), were tested as substrates. Cleavage was observed with Abz-MKRLTL-EDDnp, Abz-FRLVR-EDDnp, and Abz-PLGLLGR-EDDnp at Leu-Thr, Leu-Val and Leu-Leu/Leu-Gly bonds respectively as determined by isolation of the corresponding fragments by HPLC. Leucine at P1 seemed to be restrictive for the activity of the exocellular enzyme, but threonine (P'1) and leucine (P'2) in Abz-MKRLTL-EDDnp apparently were not essential. Also, a pair of alanines could substitute for lysine (P3) and arginine (P2) in this substrate, with a decrease in the Km values. The exocellular peptidase activity of P. brasiliensis had an optimum pH of > 9.0 and was irreversibly inhibited by PMSF, mercuric acetate and p-hydroxymercuribenzoate. Inhibition of the mercuriate compounds could be partially reversed by Cys/EDTA. E-64 [trans-epoxysuccinyl-L-leucylamido-(4-guanido)butene] was a weak and reversible inhibitor, whereas EDTA and pepstatin were not inhibitory. These results suggest that P. brasiliensis exocellular enzyme belongs to the subfamily of SH-containing serine proteinases.

Amino Acid Sequence↗
PubMed1995

Effect of germination on the protein content and on the level of specific activity of lipoxygenase-1 in seedlings of three soybean cultivars.

The effect of germination on the protein content and in the level of specific activity of lipoxygenase-1 on seedlings of Santa Rosa, FT-2 and Davis soybean cultivars were studied. Soybean seeds of the three cultivars were germinated from 0 to 72 hours in a seed germinator at 30 degrees C temperature, 100% relative humidity, and absence of light. The seeds were then frozen in liquid nitrogen, freeze-dried and milled. The lipoxygenase-1 was extracted with 0.02M thris-HCI buffer at pH = 8.2 and 13% saccharose for 30 minutes at 4 degrees C without shaking. The highest levels of specific activity of lipoxygenase-1 per milligram of flour (dry basis) in the Santa Rosa, FT-2 and Davis cultivars were observed between 18 and 36, 18 and 24, and 0 and 12 hours, respectively. The polinomial quadratic model best fits the regression analysis of the variable levels of specific lipoxygenase activity for cultivar Davis (R2 = 0.9197). Although for cultivars Santa Rosa (R2 = 0.9041)., and FT-2 (R2 = 0.7486) the 4th degree polynomial model has shown the best fit. The protein content in the three cultivars studied reached the maximum values at 48h germination. The germination induced a relative increase of the protein content but caused a reduction of the level of specific lipoxygenase-1 activity.

Germination↗
PubMed1994

Variant forms of a group I intron in nuclear small-subunit rRNA genes of the marine red alga Porphyra spiralis var. amplifolia.

A group IC1 intron occurs in nuclear small-subunit (18S) ribosomal RNA (SSU rRNA) genes of the marine red alga Porphyra spiralis var. amplifolia. This intron occurs at the same position as the self-splicing group IC1 introns in nuclear SSU rDNAs of the fungus Pneumocystis carinii and in the green alga Chlorella ellipsoidea and shares sequence identity with the Pneumocystis carinii intron in domains L1, P1, P2, and L2, outside the conserved core. Three size variants, differing in amount of sequence in L1, exist and are differentially distributed in geographically distinct populations. Preliminary data suggest that the largest variant can self-splice in vitro. Short open reading frames are present but do not correspond to known genes. Repeated nucleotide motifs, reminiscent of duplicated target sites of transposons or Alu elements, are associated with the intron and with one of the variant forms of L1. Insertions are present in nuclear SSU rDNAs of several other Porphyra species and of the red alga Bangia atropurpurea; insertionless rDNA variants also occur in several Porphyra species. Our observations are most readily explained by intron mobility, although it remains unclear how transfer could have been mediated between genomes of organisms as ecologically diverse as marine red algae, freshwater green algae, and a mammalian-pathogenic fungus.

Base Sequence↗
PubMed1992

Intramolecularly quenched fluorogenic peptide substrates for human renin.

Six intramolecularly quenched fluorogenic peptides related to the sequences Phe8 to His13, His6 to His13, and Tyr4 to His13 of the human angiotensinogen, containing o-aminobenzoyl (Abz) and ethylenediamine dinitrophenyl (EDDnp) groups at amino- and carboxyl-terminal amino acids residues, were synthesized by classical solution methods. The Leu-Val is the only bond of all obtained peptides that was hydrolyzed by human renin with different degrees of purity and was resistant to hydrolysis by pig renin and cathepsin D. The hydrolysis of Abz-His-Pro-Phe-His-Leu-Val-Ile-His-EDDnp by human renin was inhibited by a highly specific transition-state analog of angiotensinogen (IC50 = 7.8 x 10(-9) M), described by K. Iizuka et al. (1990, J. Med. Chem. 33, 2707-2714). Therefore, specific and sensitive substrates for the continuous assay of human renin in which as little as 70 microGU of human renin could be detected by Abz-Phe-His-Leu-Val-Ile-His-EDDnp were described. The optimal pHs of hydrolysis of the substrates were in the range 4 to 6.

Amino Acid Sequence↗
PubMed1992

Human pharmacokinetics and radiopharmacological studies of the myocardial perfusion agent: technetium (2-carbomethoxy-2-isocyano-propane)6+.

The myocardial perfusion agent technetium (2-carbomethoxy-2-isocyano-propane)6+ (99mTc-CPI) is unique from other cationic technetium isonitrile complexes in that it exhibits moderate washout from the heart and rapid hepatobiliary clearance in animal models and human volunteers. Dynamic imaging and HPLC analysis were performed in humans and guinea pigs to outline the pharmacological basis of its pharmacokinetics. Enzymatic hydrolysis of the terminal ester groups in blood was found to occur at a moderate rate producing new species that have been shown not to accumulate in heart tissue. However, after extraction by the heart, liver or kidneys, the 99mTc-CPI complex undergoes metabolism at a much slower rate than observed in the blood. Differences in hydrolysis rate and products obtained indicate separate mechanisms of hydrolysis occurring in blood and other organs. It is proposed that the heart washout occurring after hydrolysis produces a neutral compound which is no longer retained by the negative cytosolic and mitochondrial membrane potentials in myocardial tissue.

Adult↗
PubMed1991

Synthesis of human angiotensinogen (1-17) containing one of the putative glycosylation binding sites and its hydrolysis by human renin and porcine pepsin.

The N-terminal heptadecapeptide of human angiotensinogen (Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Val-Ile-His-Asn-Glu-Ser-Thr-NH2 ), with the C-terminal carboxyl group amidated, was synthesized in order to study the role of Asn-Glu-Ser, a putative carbohydrate binding site, on the hydrolysis by human renin. The synthesis was performed by fragment condensation using the Honzl and Rudinger azide procedure. In our conditions for azide segment condensation, histidine racemization was demonstrated to be negligible for most of the condensation reactions. Human renin liberates angiotensin I from h-angiotensinogen (1-17)-NH2 with a Km value of 3.4 x 10(-5) M, at pH 7.3 and 37 degrees being similar to h-angiotensinogen (1-13), an analog without the carbohydrate binding site. However, the Vmax value of 4.1 x 10(-9) mol/G.U. min is one order of magnitude higher. Porcine pepsin was demonstrated to cleave preferentially Leu10-Val11 bond and, surprisingly, His9-Leu10 as well.

Amino Acid Sequence↗
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↗
PubMed1983

[Considerations on the renal lobes in Gallus gallus, Indian River].

Textbooks and articles do not provide sufficient descriptions of the fowl kidney, mainly the renal lobes and their measurements. The observations of the renal lobes was carried out in 40 fowls (Gallus gallus), Indian River, 27 females and 13 males, with different ages (Grupe I: one month; Grupe II: 2 months and Grupe III: more than 3 months). We have observed that: a) there is a relative assymetry on the form and position of the renal lobes; b) the cranial lobe is the most large and the middle, the most long; and c) averages about the lobes, in relation to the both antimeres and length-width, are recorded.

Age Factors↗
PubMed1982

Inhibition of renin by conformationally restricted analogues of angiotensinogen.

[Cys(5),Cys(10)]Angiotensinogen-(5-14)-peptide analogues and homologues were synthesized, in which a disulphide bond between residues 5 and 10 stabilized a 9-->6 beta-turn proposed for the substrate. These compounds were competitive inhibitors of human and pig renins with K(i) values of the order of 10(-6)-10(-5)m, indicating that the conformation proposed for the substrate is important for the interaction with the enzyme.

Angiotensinogen↗