PubMed Health⌕ Search

Biomedical subjects

L Guerrero

Publications and source records attributed to L Guerrero.

At least 37 records · Page 2Linked to original sources
PubMed1994

Prognostic implications of clinical, electrocardiographic and hemodynamic findings in chronic Chagas' disease.

To evaluate the prognostic importance of 19 clinical, electrocardiographic and hemodynamic variables, 556 chronic chagasic patients were submitted to an extensive protocol, including left cineventriculogram and Holter monitoring, and followed for up to 15 years. The protagonist role of the magnitude of the myocardial compromise in the evolution of chagasic patients is underscored by our results, which indicated the independent prognostic value of an ejection fraction below 0.30 (P < 0.001), a heart rate higher than 89 beats/min (P < 0.01), grade IV functional capacity (P < 0.05), end systolic stress > 120 g/cm2 (P < 0.05), and end diastolic volume index > 200 ml/m2 (P < 0.05). When only patients with an ejection fraction over 0.29 were considered, variables with independent prognostic value were: the cardio-thoracic ratio (P < 0.01), functional capacity (P < 0.05) and heart rate (P < 0.05). Survival analysis demonstrated that the presence of complex (Lown III, IV) ventricular arrhythmias increased mortality significantly (P < 0.01) only in patients with an ejection fraction over 0.29. Therefore, preservation of myocardial function is the capital measure in the treatment of chronic chagasic patients.

Adult↗
PubMed1994

Asymptomatic Shigella infections in a cohort of Mexican children younger than two years of age.

The proportion of Shigella infections that occur asymptomatically in young children has not been established. A community-based cohort study of 367 infants was followed prospectively by weekly home visits from January, 1990, through December, 1991. Stool samples were collected weekly and when diarrhea occurred and were tested for Shigella and other enteropathogens. There were 2925 child months of observation and 65 episodes of Shigella infection. There were 3.1 episodes/100 child months during the warm season (May through September) and 0.97 episode/100 child months during the cold season. Shigella infections were rare during the first 6 months of life but increased with age (P < 0.0001). Overall 55% of detected infections were asymptomatic. The proportion of infections that were asymptomatic increased as age increased (P < 0.01). Symptom status was not significantly associated with Shigella species or season. All isolates from symptomatic and asymptomatic children had the 120- to 140-megadalton virulence plasmid. We conclude that infections with virulent strains of Shigella are commonly asymptomatic in Mexican children during the first 2 years of life.

Age Distribution↗
PubMed1993

Regulation of the L-arginine-dependent and tetrahydrobiopterin-dependent biosynthesis of nitric oxide in murine macrophages.

Nitric oxide is a recently discovered biomolecule with a broad range of actions. The present study investigated the regulation of nitric oxide synthase activity by dexamethasone and the cofactor tetrahydrobiopterin in murine macrophages. The influence of the tetrahydrobiopterin biosynthesis inhibitors 2,4-diamino-6-hydroxypyrimidine, an inhibitor of GTP cyclohydrolase I, and phenprocoumon, an inhibitor of sepiapterin reductase, on the synthesis of nitric oxide was investigated. Dexamethasone decreased the nitric oxide production due to direct inhibition of the induction of nitric oxide synthase and of GTP cyclohydrolase. Substitution of tetrahydrobiopterin via sepiapterin could not overcome the dexamethasone-mediated inhibition. 2,4-Diamino-6-hydroxypyrimidine abolished nitric oxide synthesis and synergized with dexamethasone, completely eliminating nitric oxide production. Phenprocoumon inhibited production of nitric oxide via interference with later steps of tetrahydrobiopterin biosynthesis. An exogenous supply of tetrahydrobiopterin through sepiapterin led to a further increase of nitric oxide production, even in fully activated macrophages. The amount of nitric oxide produced by murine macrophages is therefore limited by the amount of tetrahydrobiopterin present in the cells. Inhibitors of tetrahydrobiopterin biosynthesis could provide a novel approach for therapy of pathological conditions mediated by nitric oxide, such as septic shock.

Alcohol Oxidoreductases↗
PubMed1993

Nitric oxide synthase is not a constituent of the antimicrobial armature of human mononuclear phagocytes.

Nitric oxide synthase (NOS) has received immense interest as an antimicrobial and antitumoral effector system of mononuclear phagocytes from rodents. Because there is increasing doubt that an analogous system exists in human macrophages, NOS was reexamined in these cells. Under tightly controlled conditions, with murine macrophages as positive controls, human macrophages failed to secrete nitric oxide (< 0.1 mumol/10(6) cells/24 h), even after activation with endotoxin, interferon-gamma, granulocyte-macrophage colony-stimulating factor, tumor necrosis factor-alpha, bacteria, or proliferating lymphocytes. The discrepancy between murine and human macrophages depended on neither the anatomic source (blood, peritoneum), the agent used for activation, nor the duration of activation. NOS activity was paralleled by metabolization of L-arginine to L-citrulline. Exogenous tetrahydrobiopterin, an essential cofactor of NOS not synthesized by human macrophages, did not support NOS activity in human macrophages. Also, no NOS activity was found in cellular subfractions of human macrophages. It appears that in humans, the inducible high-output NOS is not conserved as an antimicrobial system of macrophages.

Amino Acid Oxidoreductases↗
PubMed1993

Intravenous and endobronchial administration of G4120, a cyclic Arg-Gly-Asp-containing platelet GPIIb/IIIa receptor-blocking pentapeptide, enhances and sustains coronary arterial thrombolysis with rt-PA in a canine preparation.

G4120, L-cysteine, N-(mercaptoacetyl)-D-tyrosyl-L-arginylglycyl-L-alpha- aspartyl-cyclic(1-->5)-sulfide, 5-oxide, a synthetic cyclic Arg-Gly-Asp-containing pentapeptide, has a high affinity (dissociation constant of 4 nM) for the platelet glycoprotein (GP) IIb/IIIa receptor. The effects of its intravenous or endobronchial administration on thrombolysis, reocclusion, and bleeding time prolongation induced with 0.45 mg/kg bolus injections of recombinant tissue-type plasminogen activator in combination with intravenous heparin (4,000-unit bolus and 1,000 units each hour) were studied in a canine model consisting of an erythrocyte-rich blood clot in the left anterior descending coronary artery. Coronary patency was monitored for 3 hours both by ultrasonic flow probe and by repeat coronary angiography. Four groups of six to 10 dogs were studied with intravenous infusions of 0, 0.1, 0.2, or 0.3 mg/kg G4120 over 60 minutes. G4120 at a dose of 0.3 mg/kg reduced the time to reflow from a mean control value of 45 to 8 minutes (p = 0.036) and delayed reocclusion (p = 0.001). Four groups of five or six dogs were studied with endobronchial instillation of G4120 in a randomized, blinded study design using 0, 0.13, 0.25, or 0.5 mg/kg G4120. Endobronchial G4120 at a dose of 0.5 mg/kg reduced the time to reflow from a mean control value of 52 to 7 minutes (p = 0.039) and abolished cyclic reocclusion and reflow (p = 0.008). G4120 induced a dose-related transient prolongation of the template bleeding time and inhibition of ADP-induced platelet aggregation. G4120, a synthetic low-molecular-weight GPIIb/IIIa inhibitor that may be produced by chemical synthesis, may be of clinical value as a conjunctive agent for thrombolysis in patients with ischemic coronary syndromes.

Animals↗
PubMed1992

Sodium intake does not influence the effect of verapamil in hypertensive patients with mild renal insufficiency.

Information is limited regarding the efficacy of antihypertensive drugs in patients with hypertension associated with renal insufficiency. To address this question, a group of 14 outpatients with essential hypertension and mild renal insufficiency received slow release verapamil 240 mg/day for 14 days after a 4-week washout period. Patients were randomly assigned to a low (4 g/day) or high (11 g/day) salt diet, and crossed over to the alternative diet after 7 days. 24-Hour blood pressure monitoring was performed at the end of the washout period and after 7 and 14 days during verapamil treatment. Verapamil induced a significant fall in mean 24-hour blood pressure that was similar for patients on both diets (p < 0.01). As expected, natriuresis increased significantly during high sodium intake (p < 0.01), and bodyweight fell significantly when sodium intake was reduced (p < 0.05). Meanwhile, serum creatinine and creatinine clearance remained stable. These results indicate that the antihypertensive effect of verapamil is independent of sodium intake even in the presence of mild renal insufficiency.

Blood Pressure↗
PubMed1991

Patterns of normal transvalvular regurgitation in mechanical valve prostheses.

The magnitude and spatial distribution of normal leakage through mechanical prosthetic valves were studied in an in vitro model of mitral regurgitation. The effective regurgitant orifice was calculated from regurgitant rate at different transvalvular pressure differences and flow velocities. This effective orifice area was 0.6 to 2 mm2 for three tilting disc prostheses (Medtronic-Hall sizes 21, 25 and 29) and 0.2 to 1.1 mm2 for three bileaflet valves (St. Jude Medical sizes 21, 25 and 33). In the single disc valves, Doppler color flow examination disclosed a prominent central regurgitant jet around the central hole for the strut, accompanied by minor leakage along the rim of the disc (central to peripheral jet area ratio 3.3 +/- 1.2). The bileaflet prostheses showed a peculiar complex pattern: in planes parallel to the two disc axes, convergent peripherally arising jets were visualized, whereas in orthogonal planes several diverging jets were seen. Mounting the disc and bileaflet valves on a water-filled tube allowed reproduction and interpretation of this pattern: for the bileaflet valve, the jets originated predominantly from valve ring protrusions that contained the axis hinge points and created a converging V pattern in planes parallel to the leaflets and a diverging V pattern in orthogonal planes. Similar patterns were observed during transesophageal echocardiography in 20 patients with a normally functioning St. Jude prosthesis. In 10 patients with a Medtronic-Hall valve, a dominant central jet was observed with one or more smaller peripheral jets. The median central to peripheral jet area ratio was 5 to 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1991

Kistrin, a polypeptide platelet GPIIb/IIIa receptor antagonist, enhances and sustains coronary arterial thrombolysis with recombinant tissue-type plasminogen activator in a canine preparation.

BACKGROUND: Kistrin is a 68-amino acid polypeptide from the venom of the Malayan pit viper Agkistrodon rhodostoma, which inhibits the platelet GPIIb/IIIa receptor. Its effect on thrombolysis, reocclusion, and bleeding associated with administration of recombinant tissue-type plasminogen activator (rt-PA) was studied in a canine model of coronary artery thrombosis. METHODS AND RESULTS: Coronary patency was monitored for 2 hours by ultrasonic flow probe and repeated coronary angiography. The rt-PA was given as 0.45-mg/kg bolus injections at 15-minute intervals until recanalization or to a maximum of four boluses. Four groups of four or five dogs were studied: a control group that received intravenous heparin (4,000-unit bolus and 1,000 units each hour) and three groups that received heparin and 0.48, 0.24, or 0.12 mg/kg kistrin, administered as a 10% bolus injection and an infusion during a 60-minute period. In the control group, reflow occurred in four of five dogs within 37 +/- 47 minutes but was followed by cyclic reflow and reocclusion. Kistrin at a dose of 0.48 and 0.24 mg/kg reduced the time to reflow to 6 +/- 5 and 10 +/- 3 minutes, respectively, and abolished reocclusion. With 0.12 mg/kg kistrin, reflow occurred in all four animals, within 27 +/- 23 minutes, and reocclusion occurred in two animals. Kistrin induced a dose-related prolongation of the template bleeding time: with 0.48 mg/kg kistrin, the bleeding time was prolonged from 3.8 +/- 1.3 minutes before infusion to 29 +/- 2 minutes during infusion, but it was shortened to 8.3 +/- 2.6 minutes at 90 minutes after the end of infusion. Kistrin also caused a dose-related inhibition of platelet aggregation with ADP and collagen: with 0.48 mg/kg kistrin, platelet aggregation was abolished during the infusion but had partially recovered toward the end of the observation period. Pathological examination of recanalized coronary arterial segments of dogs given 0.48 or 0.24 mg/kg kistrin revealed widely patent arteries with some platelets layered on the damaged intimal surface. CONCLUSIONS: Kistrin increases the rate and extent of thrombolysis with a reduced dose of rt-PA, and it prevents reocclusion. At an effective dose, it is associated with a transient prolongation of the bleeding time and inhibition of platelet aggregation. Kistrin may offer promise as adjunctive treatment to thrombolytic agents in patients with acute myocardial infarction.

Animals↗
PubMed1991

Tolerance to nitrendipine in patients with arterial hypertension accompanying chronic renal failure.

To test the tolerance to nitrendipine in arterial hypertension secondary to chronic renal parenchymatous disease, a group of 10 patients so diagnosed and adequately controlled with a diuretic alone or with a beta-blocker were switched to nitrendipine at a dose to insure similarly adequate control of blood pressure. Patients were followed for 1 year at monthly intervals during which blood pressure measurement and the determination of a biochemical profile were performed. During the follow-up, nitrendipine adequately controlled blood pressure and a significant fall was observed in hematocrit (p less than 0.05) and serum uric acid (p less than 0.01) values. Meanwhile, the glomerular filtration rate, determined by the creatinine clearance, did not exhibit significant changes nor did the 24-h urinary excretion of proteins. The tolerance of the drug was adequate, with two patients presenting minimal ankle edema. These results seem to indicate that nitrendipine can be safely used in patients with arterial hypertension secondary to chronic renal parenchymatous disease.

Adult↗
PubMed1991

[Ventricular mechanics and cardiac arrhythmias in patients with chagasic and primary dilated cardiomyopathy. Echo-electrocardiographic follow-up].

PURPOSE: To determine the prognostic significance of several parameters of left ventricular mechanics and of complex ventricular arrhythmias. PATIENTS AND METHODS: 184 chronic chagasic and 85 primary dilated cardiomyopathy patients were submitted to non-invasive and invasive studies, including Holter monitoring and "M" mode echocardiogram and followed for a maximum of 8 years. RESULTS: Finding of a depressed left ventricle (LV) systolic function (% AC) was the most important independent prognostic factor in both groups of patients. The presence of complex ventricular arrhythmias had an additional, but very limited, independent prognostic importance, observed only in chagasic patients with depressed LV systolic function. When patients with similar degrees of left ventricular systolic dysfunction, inadequate hypertrophy or increased afterload were compared, chagasic patients had significantly worse prognosis than those with primary dilated cardiomyopathy. This is partly attributed to higher prevalence of complex ventricular arrhythmias. CONCLUSION: The higher prevalence of complex ventricular arrhythmias in patients with chronic Chagas' disease may explain the prognostic differences between the groups.

Arrhythmias, Cardiac↗
PubMed1990

Ventricular arrhythmias and left ventricular myocardial function in chronic chagasic patients.

To study the relationship of complex ventricular arrhythmias to the presence and extent of myocardial damage, 556 chronic chagasic patients were submitted to an extensive protocol, including left ventricular cineangiography and Holter monitoring, and properly classified according to clinical, electrocardiographic and hemodynamic findings. Stages of the clinical-hemodynamic classification corresponded to increasing degrees of myocardial damage, age, prevalence and complexity of ventricular arrhythmias. Myocardial damage (particularly left ventricular dilatation) was the most important clinical factor linked to the presence of complex ventricular arrhythmias. A clear difference in terms of ventricular function was found only when arrhythmias were grouped into simple (Lown grades I and II) and complex (grades III and IV) forms. It is recommended that any classification for chagasic patients must be based on signs of myocardial involvement, instead of clinical or electrocardiographic findings alone. Evaluation should include accurate determination of left ventricular myocardial function, along with the search for the presence of complex ventricular arrhythmias and abnormalities of conduction.

Adult↗
PubMed1989

[Left ventricular mechanics in Chagas' disease and dilated cardiomyopathy: echocardiographic study].

For purposes of studying left ventricular mechanics, 184 chronic chagasic and 85 primary cardiomyopathy patients were submitted to an extensive invasive (LV cine, right and left cardiac catheterization and coronarography) and non-invasive protocol. The afterload, (mean wall stress), the contractile status (ejection fraction and circumpherential shortening) and the degree of hypertrophy (mass index) were assessed by M mode echocardiography. There was a very early increase of afterload in 8% of chagasic patients without evidences of LV myocardial involvement in the left cineventriculogram (group I-A). This increased afterload was accompanied by signs of inadequate hypertrophy in 15% of patients with early segmental myocardial damage (group IB). In contrast, ejection fraction and % circumpherential shortening were depressed only in patients with clinical evidences of congestive heart failure. Dilated primary CM patients showed similar findings, except for a more evident depression of contractility in those cases without signs of congestive heart failure (group II) and more hypertrophy than equivalent group III chagasic patients. Measurements of mean systolic wall stress and mass index are valuable parameters for identification of those patients with early increased after-load and inadequate hypertrophy which could benefit from the administration of oral vasodilators.

Adult↗
PubMed1989

[Clinical and paraclinical differences between chronic Chagas' cardiomyopathy and primary dilated cardiomyopathies].

With the purpose of establishing clinical and paraclinical differences among chronic chagasic (MCh) and primary dilated cardiomyopathies (MCDP), 96 MCh and 104 MCDP patients with abnormal ECG were submitted to a study protocol which included clinical history, routine laboratory serology for Chagas' diseases, resting ECG, Chest-X-rays, and cardiac catheterisation. Patients with congestive heart failure (CHF) had common clinical and para-clinical findings. However, chagasic patients without CHF showed more prevalence of RBBB and LAH, complex ventricular arrhythmias and more left ventricular dilation while primary dilated cardiomyopathy patients with CHF had predominantly LBBB, simple ventricular arrhythmias, atrial fibrillation and less LV dilation than MCh patients. In order to establish the prognostic value of these findings and response to modern medical therapy, prospective studies on these two groups of patients are needed.

Cardiomyopathy, Dilated↗
PubMed1987

Effect of changes in ventricular relaxation on early diastolic coronary blood flow in canine hearts.

Since the gradient between aortic pressure and left ventricular diastolic pressure is a major determinant of coronary blood flow, a change in left ventricular relaxation by its effect on early diastole could diminish early diastolic coronary flow. Two interventions that resulted in impaired left ventricular relaxation, hypothermia, and reperfusion following a left anterior descending coronary artery occlusion were studied to evaluate whether there were associated changes in coronary blood flow. With both interventions, there was a significant prolongation of left ventricular relaxation (p less than 0.01) accompanied by a significant decrease in early diastolic coronary blood flow (p less than 0.01). Verapamil did not have a significant effect on these hemodynamic changes during hypothermia. However, verapamil significantly blunted the effects of reperfusion following ischemia on ventricular relaxation (p less than 0.002) and early diastolic coronary blood flow (p less than 0.01). Thus, impaired left ventricular relaxation has an adverse impact on early diastolic coronary blood flow, which, under the condition of reperfusion following regional myocardial ischemia, can be alleviated with calcium channel blockade.

Animals↗