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Biomedical subjects

M H Borges

Publications and source records attributed to M H Borges.

9 recordsLinked to original sources
PubMed2001

Neutralization of proteases from Bothrops snake venoms by the aqueous extract from Casearia sylvestris (Flacourtiaceae).

Aqueous extract from Casearia sylvestris leaves, a typical plant from Brazilian open pastures, was able to neutralize the hemorrhagic activity caused by Bothrops asper, Bothrops jararacussu, Bothrops moojeni, Bothrops neuwiedi and Bothrops pirajai venoms. It also neutralized two hemorrhagic metalloproteinases from Bothrops asper venom. Proteolytic activity on casein induced by bothropic venoms and by isolated proteases, including Bn2 metalloproteinase from B. neuwiedi venom, was also inhibited by the C. sylvestris extract in different levels. The alpha-fibrinogen chain was partially protected against degradation caused by B. jararacussu venom, when this venom was incubated with C. sylvestris extract. We also observed that this extract partially increased the time of plasma coagulation caused by B. jararacussu, B. moojeni and B. neuwiedi venoms. C. sylvestris extract did not induce proteolysis in any substrate assayed.

Animals↗
PubMed2000

Effects of aqueous extract of Casearia sylvestris (Flacourtiaceae) on actions of snake and bee venoms and on activity of phospholipases A2.

The crude aqueous extract from the leaves of Casearia sylvestris, a plant found in Brazilian open pastures, was assayed for its ability to inhibit phospholipase A2 (PLA2) activity and some biological activities of bee and several snake venoms, and of a number of isolated PLA2s. The extract induced partial inhibition of the PLA2 activity of venoms containing class I, II and III PLA2s. When tested against the purified toxins, it showed the highest efficacy against class II PLA2s from viperid venoms, being relatively ineffective against the class I PLA2 pseudexin. In addition, C. sylvestris extract significantly inhibited the myotoxic activity of four Bothrops crude venoms and nine purified myotoxic PLA2s, including Lys-49 and Asp-49 variants. The extract was able to inhibit the anticoagulant activity of several isolated PLA2s, with the exception of pseudexin. Moreover, it partially reduced the edema-inducing activity of B. moojeni and B. jararacussu venoms, as well as of myotoxins MjTX-II and BthTX-I. The extract also prolonged the survival time of mice injected with lethal doses of several snake venoms and neutralized the lethal effect induced by several purified PLA2 myotoxins. It is concluded that C. sylvestris constitutes a rich source of PLA2 inhibitors.

Animals↗
PubMed1999

IGF-I levels rise and GH responses to GHRH decrease during long-term prednisone treatment in man.

Glucocorticoid excess is associated with a blunted GH response to GHRH. IGF-I levels in hypercortisolism are controversial and have been reported as low, normal or high. The aim of this study was to evaluate longitudinally time-dependent changes in the GH response to GHRH, IGF-I, IGFBP-3 and albumin values in patients during corticotherapy. Six patients received GHRH before and after one week and one month of prednisone administration (20-60 mg/d, orally). IGF-I, IGFBP-3 and albumin were determined in each test, at time 0. Ten normal controls were also evaluated in one occasion. There were no differences in basal GH values, GH response to GHRH, IGF-I and IGFBP-3 levels between controls and patients before starting corticotherapy. Albumin (g/l; mean+/-SE) values were lower in patients before treatment (31+/-4) than in controls (43+/-1). After one week of prednisone administration there was a significant decrease in peak GH (microg/l) levels (before: 18.8+/-7.4; 1 week: 5.0+/-1.3), which was maintained after one month (8.1+/-3.5). IGF-I (microg/l) levels increased significantly, from 145+/-23 to 205+/-52 after one week of therapy, reaching levels of 262+/-32 after one month. IGFBP-3 (mg/l) values did not increase significantly (before: 2.1+/-0.2; 1 week: 2.5+/-0.3; 1 month: 2.8+/-0.2). Albumin levels showed a significant rise both after one week (36+/-4) and one month (42+/-3) of corticotherapy. In summary, we observed a marked decrease in the GH response to GHRH after one week and one month of prednisone administration associated with an increase in circulating IGF-I and albumin values. The physiological implications of these findings are still uncertain. It is possible that glucocorticoids increase hepatic IGF-I and albumin synthesis, although other mechanisms may have a role.

Adult↗
PubMed1999

Purification and partial characterization of a new proteolytic enzyme from the venom of Bothrops moojeni (CAISSACA).

A basic serine protease which is active on casein and fibrinogen was purified from Bothrops moojeni venom using a single step chromatography on a CM-Sepharose fast flow column. The enzyme, MOO3, was not hemorrhagic and presented only a trace of blood-clotting activity. Synthetic chromogenic substrates (azoacasein and azoalbumin) where not hydrolyzed by MOO3. Using polyacrylamide gel electrophoresis at pH 4.3, MOO3 showed as a single protein band. Using sodium dodecyl sulfate-polyacrylamide electrophoresis, MOO3 behaved as a single-chain protein with an approximate mol. weight of 27,000, both in the presence and absence of beta-mercaptoethanol. Its pI was 7.8 by electrofocusing. The enzyme did not contain neutral carbohydrates and its N-terminal amino acid was alanine. The amino acid composition showed 249 residues/mole, a high content of hydrophilic amino acids and 14 half-cystine residues, which should account for 7 disulfide bonds. The protease cleaved the A-alpha chain faster than the B-beta of bovine fibrinogen and showed no effect on the delta-chain. Specific esterolytic activity of MOO3 on alpha-N-tosyl-l-arginine methyl ester was 29.64 mumol min-1 x mg-1. MOO3 represented 1.42% (w/w) of the initial desiccated venom. Its proteolytic activity was inhibited by beta-mercaptoethanol, leupeptin, phenylmethylsulphonyl fluoride and ethylenediamine tetraacetate.

Animals↗
PubMed1997

Different effects of growth hormone releasing peptide (GHRP-6) and GH-releasing hormone on GH release in endogenous and exogenous hypercortisolism.

OBJECTIVE: Chronic hypercortisolism is associated with decreased GH responsiveness to GHRH. GHRP-6 is a synthetic hexapeptide that releases GH in several species, including man. As GHRH and GHRP-6 apparently stimulate GH release by different mechanisms, we evaluated the GH responses to these peptides in patients with endogenous and exogenous glucocorticoid excess and also in control subjects. DESIGN: Six patients with endogenous hypercortisolism, nine with exogenous glucocorticoid excess and 10 normal controls were submitted to three tests, in random order, with GHRH (100 micrograms), GHRP-6 (1 microgram/ kg) or GHRP+GHRP-6, in the same doses, i.v., on separate days. MEASUREMENTS: GH was measured by immunofluorometric assay. IGF-I was determined by radioimmunoassay. Plasma glucose was measured by the glucose-oxidase technique. RESULTS: Peak GH values (mean +/- SE; microgram/l) after GHRH were significantly blunted in endogenous (2.0 +/- 0.7) and exogenous (3.6 +/- 1.2) hypercortisolaemic patients compared to controls (24.9 +/- 6.1). The endogenous group had lower peak GH values after GHRP-6 alone (7.7 +/- 1.9) or together with GHRH (18.8 +/- 5.8) than those observed in controls (GHRP-6: 22.1 +/- 3.6; GHRH+GHRP-6: 77.4 +/- 15.0) and in exogenous hypercortisolism (27.4 +/- 6.2 and 78.1 +/- 19.9). There were no differences in the GH responses to GHRP-6 alone or in combination with GHRH when controls were compared to the exogenous group. No changes in plasma IGF-I and glucose levels were observed. CONCLUSIONS: Our results suggest that hypercortisolism had a different effect on the GH-releasing mechanisms stimulated by GHRH and GHRP-6. Moreover, in endogenous hypercortisolism both GHRH and GHRP-6 pathways are affected, while in the exogenous group GHRP-6 releasing mechanisms are apparently preserved.

Adult↗
PubMed1997

Inhibition of proteases, myotoxins and phospholipases A2 from Bothrops venoms by the heteromeric protein complex of Didelphis albiventris opossum serum.

The antibothropic complex (ABC) from opossum (species Didelphis albiventris) serum was purified by chromatography on DEAE-Sephacel. It showed an acidic character and two polypeptide chains of ca. 45 kDa and 48 kDa, respectively. Lyophilized opossum serum or the ABC (100 micrograms), as well as ethylenediamine tetraacetate (0.25 mumoles) were able to completely neutralise the hemorrhagic effect of 50 micrograms of the desiccated venoms of Bothrops moojeni, Bothrops pirajai and Bothrops jararacussu. The myotoxic (100 micrograms venom in mice) and edematogenic (90 micrograms venom in rats) activities of Bothrops moojeni and Bothrops jararacussu venoms, as well as of the major myonecrotic protein (myotoxin-I) isolated from Bothrops moojeni venom, were also totally inhibited by the ABC (200 micrograms and 270 micrograms, respectively). The lyophilized opossum serum (30 micrograms) and the ABC (30 micrograms) reduced to 50% the phospholipase A2 activity of Bothrops moojeni venom (10 micrograms). The clotting activity of Bothrops alternatus and Bothrops moojeni (20 micrograms) on bovine plasma was also significantly inhibited by the ABC (60 micrograms).

Animals↗
PubMed1996

Growth hormone axis in cushing's syndrome.

All levels of the growth hormone (GH), GH binding protein (GHBP), insulin-like growth factor (IGF) and IGF binding protein (IGFBP) axis are influenced by chronic hypercortisolism. Thus, there is a blunted response to GHRH alone or together with other stimuli associated with a marked suppression of endogenous GH secretion but accompanied by normal GHBP, normal to low IGF-1 and GHBPs 1 and 3 with the correspondent 41.5 and 38.5-kD molecular forms of the latter presenting values similar to normal. These findings may suggest enhanced GH sensitivity with normal or increased IGF-1 bioavailability to the correspondent tissue receptors. In conclusion, the glucocorticoid (GC)-induced target tissue resistance can neither be attributed to the suppression of the GH axis nor to changes in circulating GHBPs 1 and 3. However, it may be related either to the described 12-to-20-kD inhibitor(s) which antagonizes postbinding IGF-1 bioactivity (gene expression) and/or by the downmodulation of activator protein-1 (Fos/Jun) activity by the GC-GC receptor complex.

Carrier Proteins↗
PubMed1993

Different effects of pyridostigmine on growth hormone (GH) response to GH-releasing hormone in endogenous and exogenous hypercortisolemic patients.

1. Somatostatin may play a role in the inhibition of growth hormone (GH) response to GH-releasing hormone (GHRH) in hypercortisolism. To examine this hypothesis we studied the effect of pyridostigmine, a cholinergic agonist that decreases hypothalamic somatostatin, on the GH response to GHRH in 8 controls, in 6 patients with endogenous hypercortisolism (3 with Cushing's disease and 3 with adrenal adenomas) and in 8 patients with exogenous hypercortisolism (lupus erythematosus chronically treated with 20-60 mg/day of prednisone). Each subject received GHRH(1-29)NH2,100 micrograms iv twice, preceded by pyridostigmine (120 mg) or placebo, orally. 2. The GH response to GHRH was significantly blunted in all hypercortisolemic patients compared to controls both after placebo (GH peak, 5.8 +/- 1.6 vs 46.2 +/- 15.9 micrograms/l, mean +/- SEM) and after pyridostigmine (15.7 +/- 5.6 vs 77.2 +/- 19.8 micrograms/l). 3. The GH response was absent in endogenous hypercortisolemic patients compared to the exogenous group, both after placebo (2.2 +/- 0.3 vs 8.5 +/- 2.4 micrograms/l) and after pyridostigmine (4.9 +/- 2.5 vs 23.8 +/- 8.7 micrograms/l). The GH release after GHRH/pyridostigmine for the exogenous group was similar to the response of controls treated with GHRH/placebo. 4. These results confirm that the GH response to GHRH is blunted in hypercortisolism, although more pronounced in the endogenous group. Pyridostigmine partially reversed this inhibition in the exogenous group. Therefore, somatostatin may play a role in the inhibition of GHRH-induced GH release in exogenous hypercortisolemic states.

Adolescent↗