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Biomedical subjects

A Chávez-Negrete

Publications and source records attributed to A Chávez-Negrete.

10 recordsLinked to original sources
PubMed2004

Starch-hemoglobin induces contraction on isolated rat aortic rings.

BACKGROUND: Blood substitutes are being developed using molecular solutions of modified free hemoglobin; however, anaphylactic reactions, severe renal toxicity, and hypertension have been reported in experimental models and human beings. Hypertension remains as an obstacle to the clinical use of most blood substitutes. Several investigators suggest that this effect is due to the interaction between nitric oxide and hemoglobin into the endothelial cells; hence, prevention of hemoglobin extravasation would avoid vasoconstriction. The forms of hemoglobin likely to prevent extravasation include polymerized and encapsulated Hb. Another alternative and significantly less expensive approach is the hydroxyethyl starch Hb-polymer. The aim of the present study was to compare the effect of hydroxyethyl-starch-hemoglobin with that of stroma-free hemoglobin on the in vitro contractile activity of aortic rings isolated from adult male rats. METHODS: The hemoglobin-based oxygen carrier was made using stroma-free hemoglobin prepared from outdated human red cells and conjugated with 10% hydroxyethyl starch 200-260 MW. The experiments were made in thoracic segments of the aortic rings incubated with hemoglobin, starch-hemoglobin or Ringer Krebs-Bicarbonate solution (RKB) during 30 min. Smooth muscle contraction with phenylephrine and subsequent inhibition of contraction with carbachol were performed before and after incubation with hemoglobin, starch-hemoglobin, or vehicle. RESULTS: Incubation with hemoglobin and starch-hemoglobin significantly increased the contractile response to phenylephrine of aortic rings compared with RKB solution. The maximal response to carbachol was significantly decreased in the aortic rings incubated with either hemoglobin or starch-hemoglobin in comparison with the RKB-incubated tissues. There were no differences between the aortic rings incubated with either hemoglobin, or starch-hemoglobin. CONCLUSIONS: These results show that there are no differences between the effects of stroma-free hemoglobin and starch-hemoglobin on the in vitro contractile activity of aortic rings isolated from adult male rats. Our findings do not support the hypothesis that an increase in the size of the hemoglobin molecule prevents hemoglobin extravasation, and the consequent vasoconstriction due to the scavenging of nitric oxide by stroma free hemoglobin in the cellular space between endothelium and smooth muscle.

Animals↗
PubMed1991

Treatment of hemorrhagic shock with intraosseous or intravenous infusion of hypertonic saline dextran solution.

The efficacy of intravenous or intraosseous infusion of 250 ml of 7.5% NaCl and 6% dextran 60 (H/H) was compared with intravenous Ringer's lactate (RL) for the initial treatment of patients with hemorrhagic shock due to upper gastrointestinal bleeding. 49 patients were randomly assigned to receive either H/H (n = 26) or RL (n = 23). In the first 16 patients with H/H and in all RL patients, solutions were infused by the intravenous route, while the intraosseous route through sternal puncture was chosen for the last 10 H/H subjects. H/H patients were analyzed together since no differences were noticed between the routes of infusion. The H/H group also received 2.3 +/- 0.7 liters of intravenous crystalloid solutions in the first hour and 4.4 +/- 0.1 liters in the 24-hour period, while RL received 3.3 +/- 0.7 and 7.3 +/- 2.4 liters, respectively. Blood pressure (BP) increased during the first 15 min in the H/H group (from 61 +/- 17/30 +/- 12 to 85 +/- 30/48 +/- 14 mm Hg) and thereafter, while remaining unchanged in the RL group (from 75 +/- 18/40 +/- 12 to 75 +/- 17/40 +/- 14 mm Hg; p less than 0.05). The differences between groups were significant throughout 24 h. Urine output and improvement of the Glasgow Coma Score were also higher in H/H patients than in the control group (p less than 0.05). There were 5 deaths in RL group and 1 in the H/H group. Sternal of peripheral vein infusion of 250 ml of 7.5% NaCl/6% dextran 60 is an effective initial treatment of hemorrhagic shock.

Blood Pressure↗
PubMed1983

HLA-DR antigens in Mexican patients with Guillain-Barré syndrome.

The distribution of HLA-DR antigens was investigated in 38 Mexican Mestizo patients with Guillain-Barré syndrome (GBS) and in 100 healthy controls belonging to the same population. IgG, IgM, IgA, CH50, C3, C4 and the number of T and B lymphocytes were also evaluated in the patients. Only DR3 was significantly increased in the patients (Yates' chi 2 = 9.943, Pc = 0.014) and the relative risk for developing the disease was 3.49. These findings support the hypothesis that DR3 or a closely linked Ir gene may play some role in the susceptibility to GBS.

Adolescent↗
PubMedDate not supplied

Influence of nopal intake upon fasting glycemia in type II diabetics and healthy subjects.

To assess if the acute hypoglycemic effect of nopal which occurs in diabetic patients also appears in healthy individuals, 500 g of nopal stems (O. streptacantha Lem.) were given orally to 14 healthy volunteers and to 14 patients with NIDDM. Serum glucose and insulin levels were measured at 0, 60, 120 and 180 minutes after nopal ingestion. A control test was performed with the intake of 400 ml of water. The intake of nopal by the NIDDM group was followed by a significant reduction of serum glucose and insulin concentration reaching 40.8 + 4.6 mg/dl (n = 14) (mean+SEM) and 7.8 + 1.5 uU/ml (n = 7) less than basal value, respectively, at 180 minutes. (P less than 0.001 vs control test). No significant changes were noticed in the healthy group as compared with the control test (P greater than 0.05). Acute hypoglycemic effect of nopal was observed in patients with NIDDM but not in healthy subjects, thus the mechanisms of this effect differs from current hypoglycemic agents.

Administration, Oral↗
PubMedDate not supplied

[Activity of Opuntia streptacantha in healthy individuals with induced hyperglycemia].

Hypoglycemia effect Opuntia streptacantha which occur in diabetic has not been found in healthy subjects. To find out if this effect appears also in healthy individuals if they are hyperglycemic, two tests were performed to 7 healthy volunteers. In both tests 500 ml of 20% dextrose were infused in two hours, 500 g of O. streptacantha were given orally before one test, and 400 ml of water as control were given before the other one. Serum glucose was measured every 30 minutes during three hours. Glucose rising was significantly (P less than 0.025) lower with Opuntia than in control test at 90 and 120 minutes (143 +/- 58 vs 193 +/- 9 and 135 +/- 25 vs 163 +/- 13 mg/dl respectively). Area under curve of glucose was also smaller in Opuntia than in control test (P less than 0.05). Hypoglycemic effect of O. streptacantha also occur in healthy subjects in hyperglycemia is present.

Administration, Oral↗
PubMedDate not supplied

[Hypoglycemic action of different doses of nopal (Opuntia streptacantha Lemaire) in patients with type II diabetes mellitus].

To assess the relationship between the doses of O. streptacantha Lem. and its acute hypoglycemic action in diabetics, eight patients with type II diabetes mellitus were studied. Four test were performed to each patient with the intake of: (a) 400 ml of water, (b) 100 g (c) 300 g and (d) 500 g of broiled stems of O. streptacantha Lem. Serum glucose was measured at 0, 60, 120 and 180 minutes. Maximal decrease of serum glucose was noticed at 180 minutes, with a mean of 2.3, 10, 30.1 and 46.7 mg/dl less than basal value with 0, 100, 300 and 500 g respectively (P = NS, less than 0.05, less than 0.001 and less than 0.001 respectively). A significant direct correlation (r = 0.690, P less than 0.001) was noticed between the doses and the hypoglycemic effect.

Administration, Oral↗