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Biomedical subjects

A M Chavez

Publications and source records attributed to A M Chavez.

17 recordsLinked to original sources
PubMed2000

Total intravenous anesthesia with a propofol-ketamine combination during coronary artery surgery.

OBJECTIVE: To evaluate the cardiovascular effects of a propofol-ketamine combination in patients undergoing coronary artery surgery. DESIGN: Prospective, randomized study. SETTING: Tertiary care teaching hospital, single center. PARTICIPANTS: Seventy-eight adult patients. INTERVENTIONS: Patients were randomly allocated to receive propofol-ketamine for induction and maintenance of anesthesia (n = 36) or fentanyl-enflurane (controls, n = 42). MEASUREMENTS AND MAIN RESULTS: Hemodynamics and other variables were recorded during and after surgery and for 24 hours in the intensive care unit. Before cardiopulmonary bypass (CPB), there was similar incidence of treatment for hypotension (42% of patients in both groups), tachycardia (propofol-ketamine, 6%; controls, 5%), and myocardial ischemia (propofol-ketamine, 3%; controls, 12%). In the propofol-ketamine group, there was a decreased requirement for inotropic agents after CPB (22% of patients) compared with controls (49% of patients; p = 0.02). There was a reduced incidence of myocardial infarctions (creatine kinase myocardial band >133 U/L) in the propofol-ketamine group compared with the control group (0% v 14%; p = 0.02; Fisher's exact test). Patients in the propofol-ketamine group were more likely to have their tracheas extubated within 8 hours of arrival in the intensive care unit compared with controls (33% v 7%; p = 0.01; Cochran-Mantel-Haenzel test). CONCLUSIONS: The propofol-ketamine combination was associated with a similar incidence of pre-CPB hypotension and ischemia, a decreased need for inotropes after CPB, an earlier time to tracheal extubation, and a reduced incidence of myocardial infarctions compared with controls.

Anesthesia, Intravenous↗
PubMed1999

Cytokine-induced intestinal epithelial hyperpermeability: role of nitric oxide.

OBJECTIVE: Incubation of enterocytic monolayers with interferon (IFN)-gamma increases nitric oxide (NO) production and permeability, but NO synthesis inhibitors ameliorate the development of IFN-gamma-induced hyperpermeability. Induction of inducible nitric oxide synthase (iNOS), an isoform of the enzyme responsible for NO biosynthesis, is often enhanced by the synergistic effects of multiple cytokines. Moreover, many of the cytopathic effects of NO are mediated by peroxynitrite, which is produced by the reaction of NO with superoxide radical anion. In the present study, we sought to determine whether combinations of several proinflammatory cytokines, including IFN-gamma, interleukin-1beta, and tumor necrosis factor-alpha, have synergistic effects on the induction of iNOS expression and/or hyperpermeability to hydrophilic solutes in cultured enterocytic monolayers. We also assessed the effects of aminoguanidine (a relatively selective iNOS inhibitor), L-N(G)-monomethyl arginine (an isoform-nonselective NO synthase inhibitor), and Tiron (a superoxide radical anion scavenger) on the development of cytokine-induced hyperpermeability. DESIGN: Caco-2 monolayers were incubated under control conditions or with IFN-gamma, interleukin-1beta, or tumor necrosis factor-alpha alone, pairwise combinations of these cytokines, or all three cytokines together (cytomix; CM). iNOS messenger RNA (mRNA) expression was assessed using Northern blot analysis. The permeability of Caco-2 monolayers growing on permeable supports in bicameral chambers was assessed by measuring the apical-to-basolateral flux of fluorescein disulfonic acid. The concentration of nitrate plus nitrite in culture supernatants, an indirect measure of NO production, was determined using the Griess reaction. RESULTS: After 24 hrs of incubation, up-regulation of iNOS mRNA expression was evident only in cells exposed to IFN-gamma-containing formulations. Expression of iNOS mRNA was far greater in cells incubated with CM than in cells treated with IFN-gamma alone or either of the two-component IFN-gamma-containing cytokine combinations. Compared with IFN-gamma, CM resulted in a higher rate of NO production over 48 hrs of incubation. The permeability of Caco-2 monolayers increased by approximately six-fold and approximately 20-fold after incubation for 48 hrs with IFN-gamma alone and CM, respectively. The increase in permeability induced by incubation with CM was significantly ameliorated by the addition of aminoguanidine, L-N(G)-monomethyl arginine, or Tiron. CONCLUSIONS: IFN-gamma-containing combinations of cytokines are potent inducers of iNOS in cultured enterocytic monolayers. Peroxynitrite may be an important mediator of cytokine-induced gut epithelial hyperpermeability.

1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium ↗
PubMed1999

Acquired interferon gamma responsiveness during Caco-2 cell differentiation: effects on iNOS gene expression.

BACKGROUND: Impairment of intestinal barrier function occurs under a variety of inflammatory conditions and is mediated at least in part by interferon gamma (IFN-gamma) induced nitric oxide (NO) production. Previous in vivo studies have shown that systemic lipopolysaccharide treatment caused an induction of the rat inducible nitric oxide synthase (iNOS) mRNA primarily in villus cells, rather than in undifferentiated crypt cells. AIMS: To examine iNOS induction by IFN-gamma in vitro as a function of enterocyte differentiation. METHODS: Preconfluent and postconfluent Caco-2 cells were treated with IFN-gamma in the presence or absence of various inhibitors. Northern analyses were performed to assess the magnitude of iNOS mRNA induction. IFN-gamma receptor mRNA and protein levels were determined. RESULTS: iNOS mRNA induction by IFN-gamma occurred at two hours and was not blocked by cycloheximide, indicating that it is an immediate early response. iNOS induction and nitrite/nitrate increases were inhibited by dexamethasone and pyrrolidine dithiocarbamate, supporting an important role for the NF-kappaB transcription factor in this process. The stimulated iNOS induction was seen almost exclusively under conditions of cellular differentiation-that is, in postconfluent Caco-2 cells. This increased IFN-gamma responsiveness seen in postconfluent Caco-2 cells correlated with an increased expression of IFN-gamma receptor, whereas T84 and HT-29 cells did not show any significant alterations in either iNOS induction or IFN-gamma receptor levels as a function of postconfluent growth. CONCLUSIONS: With regard to iNOS mRNA induction, IFN-gamma responsiveness is acquired during Caco-2 cell differentiation, perhaps related to an increase in the numbers of IFN-gamma receptors.

Blotting, Northern↗
PubMed1998

A re-evaluation of the mechanism of action of botulinum toxin on facial movement disorders in man.

Despite a lot of research aimed at clarifying the mechanism of action of botulinum toxin, mostly at supraspinal levels, a complete understanding of it is still elusive. However, recent investigations, including our own, allow us to suggest that, in facial muscles, the effects of botulinum toxin are not only in the neuromuscular junctions affecting the acetylcholine release but also modify the sensory inflow with subsequent changes on the muscle spindle-gammamotoneuron system.

Animals↗
PubMed1994

Endobronchial adenocarcinoma with endometrioid features and prominent neuroendocrine differentiation. A variant of fetal adenocarcinoma.

An endobronchial tumor, resected from a 77-year-old man, had an endometrioid histologic pattern consistent with fetal adenocarcinoma. A distinctive feature of the neoplasm was prominent neuroendocrine differentiation, including single, discrete neuroendocrine cells; aggregates of neuroendocrine cells resembling miniature carcinoid tumors; and a single focus of undifferentiated small cell carcinoma. Immunohistochemical staining of neuroendocrine cells revealed the presence of neuron-specific enolase, chromogranin, somatostatin, insulin, and serotonin. The heterogeneous cell populations caused problems in differential diagnosis and histologic classification. This case demonstrates that fetal adenocarcinoma may occur as a central endobronchial mass and express a variable degree of neuroendocrine differentiation.

Adenocarcinoma↗
PubMed1990

Blood conservation.

The importance of blood conservation to minimize homologous blood use after cardiac surgery is well-accepted. The most successful programs to this end are the products of an integrated approach to blood conservation that begins with preoperative patient screening and carries through the postoperative period. Salvage and reinfusion of shed blood both intra- and postoperatively are important components of any such program. Other practices that help reduce blood loss and decrease the use of banked blood are also important. It is the combination of techniques and a consistent philosophy regarding the importance of blood conservation that will yield the best results. Programs that decrease the use of banked blood help today's cardiac surgeon provide safer, less costly operations for his or her patients.

Blood Banks↗
PubMed1988

Applicability of mitral valvuloplasty techniques in a North American population.

Records of 520 patients who underwent mitral valve operations were reviewed to determine the pathophysiology, etiology, anatomy of the valve lesion and use of valvuloplasty techniques. Pure mitral regurgitation, present in 269 patients (52%), was the most common lesion while rheumatic valvulitis, seen in 286 patients (55%), was the most common etiology. Degenerative lesions were found in 168 patients, 33% of the total and 63% of the pure mitral regurgitation group. Two-hundred seventy patients (52%) were treated with valvuloplasty techniques. The incidence of reconstructive procedures was determined for each of the various patient subsets. Overall hospital mortality was 5.6% in the series: 8.4% for mitral replacement compared with 3% for mitral valvuloplasty (p = 0.007). Among patients undergoing primary isolated mitral procedures, hospital mortality for replacement was 7.5% compared with 1.4% for valvuloplasty (p = 0.018). Mitral valvuloplasty seems to provide a therapeutic alternative applicable to the spectrum of mitral valve pathology seen in a North American population.

Female↗
PubMed1988

Surgery for mitral prolapse.

Mitral valve prolapse is an increasingly common etiology among patients presenting for mitral valve surgery. From 1985 through 1987, a total of 457 patients underwent surgery for pure mitral regurgitation. Of these, 304 (67%) had underlying mitral prolapse, 57 (12%) had rheumatic valvulitis, 36 (8%) had underlying ischemic disease, and 22 (5%) had bacterial endocarditis. The anatomic disturbance in the patients with prolapse was chordal rupture in 189 (62%), chordal elongation in 69 (23%), and isolated annular dilatation in 46 (15%). Valvuloplasty techniques were used in 294 patients (64%) overall. Among those with mitral prolapse, 208 patients (68%) underwent reconstructive procedures. Operative mortality for the entire group was 7% and for the valvuloplasty group it was 4%. We conclude that 1. in our patient population mitral prolapse is the most frequent etiology among patients requiring surgery for mitral regurgitation; 2. valvuloplasty techniques are applicable in the majority of these patients; 3. valvuloplasty can be performed with low operative mortality. Over the long term, available results indicate good clinical status and low rates of reoperation and thromboembolic events for patients who have undergone mitral valvuloplasty.

Follow-Up Studies↗
PubMed1987

Elective coronary surgery.

The goal of providing patent grafts distal to important coronary stenoses remains unchanged. Results of bypass grafting show the influence of refined technique, improved technology, and the longer followup now available. Coronary artery bypass is now routinely performed with low morbidity and mortality. Late attrition of saphenous vein grafts with concomitant deterioration of patients' clinical status has been increasingly recognized. The internal mammary graft, with its superior patency and impact on length and quality of survival, is gaining wider acceptance. Increased use of the mammary artery graft and extension of its use with bilateral and sequential grafting patterns are an important trend in the current practice of coronary surgery.

Angina Pectoris↗
PubMed1986

Results of mitral valve reconstruction.

To evaluate the early results of mitral valve reconstruction for mitral insufficiency, 117 consecutive cases were analyzed. Sixty-four (57.7%) of the patients were men, and the mean age was 60 +/- 13 years (range 18 to 85). Eighty-nine (76%) of the patients were in NYHA functional class III or IV preoperatively. The cause of the mitral disease was degenerative in 94 (80%) and rheumatic in 13 (11%) patients. Isolated mitral valve repair was performed in 56 patients (47.9%); the remainder underwent associated procedures that included myocardial revascularization in 38 (32.5%). Ninety-nine (85%) underwent a ring annuloplasty but in only seven (6%) was this the only repair technique. Resection of the posterior leaflet was performed in 41 (35%). There were five operative deaths (4.3%); one (1.8%) occurred after isolated repair and four (6.5%) after repair with associated procedures. All deaths occurred in patients greater than 65 years of age who were in NYHA functional class III or IV. Mean follow-up was 13.5 months (range 1 to 62). Two year actuarial survival was 90.6%. Three patients required reoperation (incidence of 2.5% per patient-year). Two patients sustained embolic events (incidence of 1.6% per patient-year). There were no anticoagulant-related complications. After surgery, 100 survivors (96.2%) were in NYHA functional class I or II.

Adolescent↗
PubMed1982

Bioprosthetic valvular failure. Clinical and pathological observations in an experimental animal model.

We compared the clinical, hemodynamic, and morphological findings in 18 young sheep in which porcine valvular bioprosthesis (eight animals) and bovine pericardial bioprostheses (10 animals) were implanted in the tricuspid position. At the time of terminal elective studies (mean of 5.2 +/- 0.2 months after implantation), six animals had ascites, 16 had hepatic congestion, and four had bioprosthetic valvular infection. Hemodynamic studies (n = 10) showed that the tricuspid transvalvular mean diastolic gradients were not different at implantation and at termination of the study (4.7 +/- 0.8 versus 4.9 +/- 0.9 mm Hg); however, tricuspid valve end-diastolic gradients increased from 1.2 +/- 0.6 to 3.9 +/- 0.5 mm Hg (p less than 0.01). Each of the 18 valves had calcific deposits. Quantitative studies revealed that implanted porcine valvular bioprosthesis (n = 7) contained a mean of 323 +/- 165 mg of calcium/gm of dry weight of cuspal tissue, in contrast to 0.2 mg/gm in unimplanted porcine valvular prostheses. Similarly, implanted bovine pericardial bioprostheses (n = 6) contained a mean of 421 +/- 115 mg of calcium/gm of dry weight of cuspal tissue, in contrast to 0.3 mg/gm im unimplanted bovine pericardial bioprostheses. Morphological findings in both types of bioprostheses included calcific deposits, collagen degeneration, leaflet immobilization and retraction, and fibrous sheaths. The latter were more extensive in bovine pericardial bioprostheses than in porcine valvular bioprostheses. We conclude: (1) that the pathological alterations which develop in bovine pericardial bioprostheses are generally similar to those in porcine valvular bioprostheses, but may be more severe; (2) that these alterations lead to physiological and clinical sequelae similar to those of bioprosthetic valvular failure in human subjects; and (3) that young sheep constitute an excellent experimental model for in vivo testing of bioprosthetic cardiac valves.

Animals↗
PubMed1982

Failure of porcine aortic and bovine pericardial prosthetic valves: an experimental investigation in young sheep.

Seventeen porcine aortic and 10 bovine pericardial bioprosthetic valves were implanted in the tricuspid position in 27 young sheep. Clinical, hemodynamic and morphologic evaluations were performed after a mean of 4.7 +/- 0.3 months (range 3-7 months) after implantation. Eight sheep developed ascites (five with porcine aortic and three with bovine pericardial bioprosthetic valves); all 27 sheep had microscopic evidence of hepatic congestion. Three porcine and three bovine valves became infected. Hemodynamic studies (n = 15) performed immediately after implantation and at the time of terminal elective studies showed that tricuspid valve end-diastolic gradients increased from 0.7 +/- 0.4 mm Hg to 4.5 +/- 0.5 mm Hg (p less than 0.01). All 27 valves had calcific deposits. By quantitative analyses, unimplanted cuspal tissue (n = 9) had 0.6 +/- 0.1 mg/g of calcium/g tissue dry weight; explanted porcine aortic valves (n = 16) had 182 +/- 74 and bovine pericardial valves (n = 6) 421 +/- 115 mg/g of calcium/g of tissue dry weight (NS for porcine aortic vs bovine pericardial valves). Morphologic findings were similar in both porcine aortic and bovine pericardial valves, and consisted of calcific deposits, collagen degeneration, microthrombi and fibrous sheaths. These findings are almost identical to those associated with bioprosthetic valvular failure in humans. In our experimental study, we found no significant differences in the development of calcification in porcine aortic and bovine pericardial bioprosthetic valves.

Animals↗
PubMedDate not supplied

Contralateral early blink reflex in multifocal motor neuropathy.

Multifocal motor neuropathy (MMN) is a clinical entity affecting the peripheral nerve system mainly. We present here a Colombian man, 37 year-old, who presented MMN, and interestingly, displayed abnormal responses in the blink reflex after electrical stimulation of the supraorbital nerves. These findings allow us to suggest that the lesion distribution in MMN mostly the subclinical one, seems to be more widespread than usually thought.

Adult↗