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Biomedical subjects

R Hernandez

Publications and source records attributed to R Hernandez.

At least 109 records · Page 6Linked to original sources
PubMed1994

Intravascular ultrasound imaging of angiographically normal coronary segments in patients with coronary artery disease.

Intravascular ultrasound imaging (IVUS) constitutes a new diagnostic technique that provides unique information concerning arterial wall structure and luminal dimensions. To assess the anatomic features of angiographically normal coronary arteries in patients with coronary artery disease, 25 patients (aged 61 +/- 9 years) underwent an IVUS examination before coronary angioplasty. A mechanical (20 MHz) IVUS system was used. Atherosclerotic plaques were identified by IVUS as well-defined structures of variable echodensity protruding into the coronary lumen or disrupting normal coronary wall architecture. Five (20%) patients had minor angiographic irregularities proximal to the target lesion, and all 5 had plaque on IVUS. In the remaining 20 patients the coronary segments proximal to the target lesion were angiographically normal. Of these, IVUS demonstrated the presence of plaque in 16 (80%) patients at 19 different angiographic sites (3 lipidic, 13 fibrotic, 3 calcified). Fifteen plaques had a semilunar appearance and did not disrupt luminal contour, but four clearly protruded into the coronary lumen. Six plaques were located in the left main artery, 4 in the left anterior descending artery, 4 in the left circumflex artery, 4 in the right coronary artery, and 1 in a vein graft. On quantitative angiography, luminal diameter, at sites angiographically normal but with plaque on IVUS, was 3.6 +/- 1 mm. At these sites, both minimal luminal diameter (3.5 +/- 1 mm) and maximal luminal diameter (4.3 +/- 1 mm) on IVUS correlated (r = 0.59 and r = 0.61, respectively) with angiographic measurements (p < 0.05). No complications resulted from the IVUS study.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗
PubMed1994

Leukotriene C4 regulation of splanchnic blood flow during ischemia.

The role of endogenous splanchnic eicosanoids in mediating splanchnic vasoconstriction induced by the leukotriene C4 (LTC4) was examined during mild hemorrhage/reperfusion injury. Male Sprague-Dawley rats were anesthetized and subjected to sham or acute hemorrhage for 30 minutes, to 30 mm Hg, followed by blood reperfusion (SK+R). The superior mesenteric artery was cannulated and removed with its end-organ intestine (SV+SI preparation) and perfused in vitro with oxygenated Krebs-Henseleit buffer. Perfusion pressure was constantly recorded. Net SV+SI release of 6-keto-PGF1 alpha, PGE2 and thromboxane B2 were analyzed by enzyme immunoassay after LTC4 stimulation. Leukotriene C4 increased perfusion pressure and decreased the ratio of 6-keto-PGF1 alpha to thromboxane release (but not PGE2 to thromboxane B2) in the sham group. Hemorrhage/reperfusion increased perfusion pressure and decreased the ratio of 6-keto-PGF1 alpha to thromboxane B2. Mild hemorrhage/reperfusion increased LTC4-induced splanchnic vasoconstriction in part by decreasing the release ratio of endogenous splanchnic PGI2 to thromboxane B2.

Analysis of Variance↗
PubMed1994

Pentoxifylline protects splanchnic prostacyclin synthesis during mesenteric ischemia/reperfusion.

This study examines the hypothesis that pentoxifylline protects splanchnic PGI2 synthesis during severe mesenteric ischemia/reperfusion injury. Anesthetized Sprague-Dawley rats (300 grams) were subjected to sham or superior mesenteric artery occlusion for 20 minutes followed by 30 minutes of reperfusion. The ischemia/reperfusion groups received either enteral allopurinol (10 mg/kg) daily for 5 days prior to ischemia, PTX (50 mg/kg) 10 minutes prior to ischemia or carrier. The superior mesenteric artery was cannulated and removed with its intact intestine (SV + SI). The SV + SI was perfused in vitro with oxygenated Krebs buffer. The venous effluent was collected and assayed for release of 6-keto-PGF1 alpha, PGE2 and thromboxane B2 by enzyme immunoassay. Severe mesenteric ischemia/reperfusion decreased SV + SI 6-keto-PGF1 alpha release by 40% compared to the sham group but did not alter release of PGE2 or thromboxane B2. Pretreatment of the animals with PTX and not allopurinol preserved SV + SI 6-keto-PGF1 alpha release at all times of perfusion to a level similar to the sham group. These data showed that severe mesenteric ischemia/reperfusion injury abolished release of endogenous splanchnic PGI2. PTX exerted a protective effect against severe mesenteric ischemia/reperfusion injury by maintaining release of splanchnic PGI2, a potent endogenous splanchnic vasodilator.

Allopurinol↗
PubMed1994

Coronary stenting for acute coronary dissection after coronary angioplasty: implications of residual dissection.

OBJECTIVES: The aim of this study was to assess the implications of residual coronary dissections after stenting. BACKGROUND: Coronary stenting is currently used in selected patients with coronary dissection after angioplasty. However, in some patients the total length of the dissection may not be completely covered with the device. METHODS: Forty-two consecutive patients (mean [+/- SD] age 58 +/- 11 years; 39 men, 3 women) undergoing stenting for a major coronary dissection after angioplasty were studied. RESULTS: Thirty (67%) coronary dissections were small (< or = 15 mm), and 29 (64%) were occlusive (Thrombolysis in Myocardial Infarction [TIMI] flow grade < or = 2). In 3 patients, coronary stenting was unable to open large occlusive dissections, but a good angiographic result was obtained in 39 patients (93%). After stenting, 22 of these patients (56%) had no visible residual dissections, and 13 (33%) had small and 4 (10%) had large residual dissections. These residual dissections were stable and did not compromise coronary flow. In a repeat angiogram (24 h later) the stent was patent in all 39 patients. However, two patients experienced a subacute stent occlusion. Of the remaining 37 patients, 36 (97%) had a late angiogram after stenting. Quantitative angiography revealed a reduction in minimal lumen diameter at the stent site (2.6 +/- 0.4 vs. 2 +/- 0.7 mm, p < 0.05) and a trend toward improvement in vessel diameter at the site of the previous residual dissection (1.7 +/- 0.6 vs. 1.9 +/- 0.5 mm, p < 0.1). The angiographic image of residual dissection disappeared in all patients. These factors provided a rather smooth angiographic appearance at follow-up. The four patients with large residual dissections after stenting did not have restenosis and were asymptomatic at last visit. CONCLUSIONS: Coronary stenting is effective in the management of acute coronary dissections after angioplasty. In this setting, small residual dissections are frequently seen but have a good outcome and disappear at follow-up. Large residual dissections may have a good outcome if coronary flow is not impaired and no residual stenosis is visualized.

Acute Disease↗
PubMed1994

Long-term outcome of coronary angioplasty in elderly patients with post-infarction angina.

The long-term clinical and angiographic outcome of 76 elderly (> or = 65 years) patients undergoing coronary angioplasty (PTCA) (83 lesions attempted) for post-infarction angina (PIA) (group I) was compared with that of 83 elderly patients undergoing PTCA (105 lesions) for stable angina (group II). Age (70 +/- 4 years), gender (70% male) and major demographic variables were similar in both groups. The mean left ventricular ejection fraction was 56 +/- 14% in group I vs 67 +/- 14% in group II (P < 0.01). In group I, PTCA was performed more frequently for lesions located in the right coronary artery (35% vs 18%, P < 0.01) and less frequently in the left circumflex artery (12% vs 26%, P < 0.05). Although the percentage of lesions with thrombi was higher in group I (16% vs 2%, P < 0.001), the rate of angiographic success was similar in both groups: 94% (78/83 lesions) in group I vs 93% (98/105) in group II (ns). PTCA was successful in 67 patients (88%) in group I and in 74 (89%) in group II (ns). The rate of major complications was also similar in both groups (4%). Restenosis occurred in 36% vs 31% of the lesions in groups I and II respectively (mean time to angiographic follow-up 7 +/- 2 months) (proportion of cases with a repeat angiography: 79% in group I and 72% in group II). Restenosis was asymptomatic in 57% vs 50% of the patients respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Acute coronary closure complicating intravascular ultrasound examination.

A patient with an excellent angiographic result after directional atherectomy suffered an acute coronary closure during an intravascular ultrasound study performed after the intervention. Intravascular ultrasound revealed a large medial dissection which could be successfully managed only with intracoronary stenting. The pathogenesis and implications of this rare major complication are discussed.

Aged↗
PubMed1994

Resistance to fracture of endodontically treated premolars restored with new generation dentine bonding systems.

MOD cavities in 60 endodontically treated teeth were restored using six different methods. Copper rings were filled with commercial hard-setting cement and the teeth were placed up to the level of the cemento-enamel junction. The teeth were grouped according to restorative method, mounted in an Instron TT machine, and the buccal walls subjected to a slowly increasing compressive force until fracture occurred. The force of fracture of the walls of each tooth was recorded and the results in the various groups compared. All teeth fractured in a similar manner irrespective of the restorative method used. All groups restored with the newer bonding system had higher resistance to fracture than those restored with an acid etch chemically cured composite resin technique. The groups restored with Den-Mat Tenure Core Paste or a Variglass VLC base and Prisma APH were significantly stronger than the acid etch Concise restored teeth (P < 0.05). No statistically significant differences were found between the other groups (P > 0.05).

Acrylic Resins↗
PubMed1994

Accumulation of glutamate by Salmonella typhimurium in response to osmotic stress.

Salmonella typhimurium accumulates glutamate in response to osmotic stress. Cells in aerobic exponential growth have an intracellular pool of approximately 125 nmol of glutamate mg of protein-1. When cells were grown in minimal medium with 500 mM NaCl, KCl, or sucrose, 290 to 430 nmol of glutamate was found to accumulate. Values were lower when cells were harvested in stationary phase. Cells were grown in conventional medium, harvested, washed, resuspended in the control medium or in medium with osmolytes, and aerated for 1 h. With aeration, glutamate was found to accumulate at levels comparable to those observed in exponential cultures. Antibiotics inhibiting protein synthesis did not affect glutamate accumulation when cells were aerated. Strains with mutations in glutamate synthase (glt) or in glutamate dehydrogenase (gdh) accumulated nearly normal levels of glutamate under these conditions. A double (gdh glt) mutant accumulated much less glutamate (63.9 nmol mg of protein-1), but a 1.9-fold excess accumulated when cells were aerated with osmotic stress. Methionine sulfone, an inhibitor of glutamate synthase, did not prevent accumulation of glutamate in cells aerated with osmotic stress. Glutamate dehydrogenase is thought to have minimum activity when ammonium is limiting. Resuspending cells with limiting ammonium reduced glutamate production but did not eliminate accumulation of excess glutamate when cells were osmotically stressed. Amino oxyacetic acid, an inhibitor of transamination reactions, did not prevent accumulation of excess glutamate.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Proteins↗
PubMed1994

Differing effects of anesthetics on splanchnic arterial blood flow during hemorrhagic shock.

The effect of anesthesia on splanchnic blood flow was examined during hemorrhagic shock and resuscitation. Sprague-Dawley rats were anesthetized with the inhalation anesthetic, methoxyflurane, or pentobarbital (65 mg/kg). Transonic Doppler flow probes were placed around the superior mesenteric artery (SMA) and the abdominal aorta, and the animals were subjected to acute hemorrhage (or sham) to 30 mmHg for 90 min followed by 30 min of resuscitation with shed blood (n = 6/group). At 90, 105, and 120 min, sham animals in both anesthetic groups showed comparable blood pressures with a 50% decrease in SMA and aortic blood flow. Acute hemorrhage decreased SMA blood flow by 94.5 +/- 0.01 and 86.0 +/- 2.8%, respectively, in the pentobarbital and methoxyflurane groups, with similar changes occurring in aortic blood flow. During resuscitation, arterial pressure remained significantly depressed and SMA blood flow decreased by 65% in the pentobarbital group, whereas blood pressure returned to control levels and SMA blood flow increased to 56% of control values (P < 0.001) in the methoxyflurane group. The findings indicate that the choice of anesthetic agent may significantly impact splanchnic blood flow and needs to be taken into account when designing experiments examining effects of hemorrhagic shock.

Anesthetics↗
PubMed1994

Halifax interlaminar clamps for posterior atlanto-axial arthrodesis with spinal fusion by "H" bone+graft.

The use of Halifax interlaminar clamps in posterior arthrodesis for atlanto-axial instabilities has recently been reported. The four Anderson II fractures submitted were surgically treated by posterior arthrodesis with Halifax clamps and bilateral "H" shaped bone-grafts obtained from the iliac crest. Only in the first case--initially treated without fusion--a review of the system became necessary due to the loosening of one clamp. No post-operative neurological complications appeared and non malunion or nonunion occurred at follow-up. Posterior arthrodesis with Halifax clamps does not involve any complication connected with the use of metal wire and the association of posterior fusion by lateral "H" shaped bone grafts ensures a stable and physiological reduction of dens fractures and atlanto-axial luxations/subluxations often associated.

Adult↗
PubMed1994

Cruciate paralysis from a Jefferson's fracture. Report a case and review of the literature.

A case of post-traumatic cruciate paralysis with a Jefferson's fracture was observed in a 54-year-old patient who fell accidentally. Cruciate or Bell's paralysis is a condition caused by incomplete cervical spinal cord lesion linked to focal and reversible damage of the pyramidal tract at the level of the decussation. The patient was treated by S.O.M.I. brace and a Philadelphia collar with a complete neurological restitution.

Cervical Atlas↗
PubMed1994

Emergency medical services development in the state of Louisiana.

Management of Emergency Medical Services has been sadly forgotten over the years in the state of Louisiana. A new task force which was formed over a year ago is now beginning to formulate a direction for the future of EMS in this state. At its last Annual Meeting, the LSMS adopted a resolution to support the work and decisions made by that task force. The EMS task force pulled together firefighters, emergency medical technicians, ambulance employees, and a group of physicians representing the specialities of trauma, emergency medicine, and pediatrics. Subcommittees were formed to address legislation, licensure, education, medical control, and pediatric issues. Definitive direction for the Bureau of EMS has been formulated with the aid of the task force and its various subcommittees. The LSMS as a whole supports this initiative; however, for it to succeed, the entire membership must understand the importance of EMS to everyone in the state. Good out-of-hospital care will determine whether a person gets early thrombolytic care, whether early defibrillation is available at their sides, and whether their child is treated with "pediatric appropriate" approaches to medical care. The life saved could be important to any one of us. The purpose of this article is to acquaint the membership with what EMS is, what the condition of EMS in Louisiana is, and what the progress of the EMS task force has been.

Education, Medical↗
PubMed1994

Liquid ventilation provides uniform distribution of perfluorocarbon in the setting of respiratory failure.

BACKGROUND: We evaluated the effect of perfluorocarbon liquid ventilation (LV) on gas exchange and pulmonary function in the setting of respiratory failure and the distribution of the ventilating medium during LV when compared to gas ventilation (GV). METHODS: Ten sheep, 17.3 +/- 4.2 kg in weight, underwent oleic acid induction of lung injury followed by either GV (n = 5) or perfluorocarbon LV (n = 5). After 1 hour animals were killed, and chest computed tomographic (CT) imaging was performed. Average CT attenuation number was assessed as an indicator of the distribution of gas or perfluorocarbon in the dependent (posterior) and nondependent (anterior) zones of the lung (air = -1000; soft tissue = 0; perfluorocarbon = +2300 Hounsfield units [H]). RESULTS: Significant increases in PaO2 (LV = 298 +/- 76 mm Hg, GV = 43 +/- 18 mm Hg, p < 0.001), SvO2 (LV = 74% +/- 6%, GV = 32% +/- 18%, p < 0.01), and lung compliance (LV = 1.65 +/- 0.50 ml/cm H2O/kg, GV = 0.58 +/- 0.06 ml/cm H2O/kg, p < 0.01) were observed. Significant decreases in physiologic shunt (LV = 24% +/- 6%, GV = 62% +/- 14%, p < 0.01) were noted. CT attenuation data showed the presence of minimal gas ventilation in the dependent regions during GV although the nondependent regions remained well aerated (CT attention number during GV: ND = -654 +/- 160 H; D = -92 +/- 160 H, p < 0.0001). During LV, there was a fairly homogenous distribution of perfluorocarbon in the lungs (CT attenuation number during LV: D = 1071 +/- 330 Hounsfield units; ND = 1112 +/- 287 Hounsfield units; p = 0.240). Lung biopsy analysis in the LV animals was consistent with a reduction in intraalveolar hemorrhage, intraalveolar edema, and the inflammatory infiltrate. CONCLUSIONS: On the basis of the data, we conclude that in this lung injury model, (1) the distribution of the ventilating medium is uniform during LV when compared to GV, (2) LV improves gas exchange and pulmonary function, and (3) histologic evidence of lung injury is reduced after LV when compared to GV.

Animals↗
PubMed1994

Increased splanchnic prostacyclin synthase and cyclooxygenase content and activity during ischemia is due to new protein synthesis.

BACKGROUND: This study examines the hypothesis that the exaggerated splanchnic release of prostacyclin is due to new synthesis of both cyclooxygenase and prostacyclin synthase (PS) in the ileum muscularis/serosa. METHODS: Sprague-Dawley rats were anesthetized and subjected to acute hemorrhage to 30 mm Hg for 30 minutes (shock) or sham shock. The superior mesenteric artery (SMA) was cannulated and removed with its end-organ intestine and perfused in vitro with Krebs-Henseleit buffer with and without cycloheximide (50 micrograms/ml) or indomethacin (20 micrograms/ml). Venous effluent was analyzed for eicosanoids by radioimmunoassay. The SMA, aorta and ileal mucosa, and muscularis/serosa were analyzed for PS and cyclooxygenase content by immunoblot analysis. RESULTS: The sham splanchnic bed released threefold more 6-keto-PGF1 alpha than prostaglandin E2 and thromboxane. Acute ischemia increased splanchnic release of 6-keto-PGF1 alpha threefold compared with sham, which was abolished by cycloheximide or indomethacin treatment. Acute ischemia increased content of PS and cyclooxygenase in the ileal muscularis/serosa twofold and PS in the aorta and SMA by 50%. CONCLUSIONS: Acute ischemia increased release of 6-keto-PGF1 alpha, which was dependent on new protein synthesis. The immunoblot data suggest that the location of the increased enzymes responsible for increased 6-keto-PGF1 alpha release is the ileal muscularis/serosa and in the aorta and SMA.

Animals↗
PubMed1993

Percutaneous mitral valvuloplasty with severe pulmonary artery hypertension.

The aim of this study was to assess the initial and midterm outcome of patients with severe pulmonary hypertension undergoing percutaneous mitral valvuloplasty (PMV). Accordingly, the baseline characteristics, immediate results and follow-up of 64 consecutive patients with severe pulmonary artery hypertension (systolic pulmonary artery pressure > or = 60 mm Hg on cardiac catheterization) (group I) were analyzed and compared with those of 194 consecutive patients with lower pulmonary pressures (group II). Patients in group I were more symptomatic (New York Heart Association functional class > or = III, 72 vs 40%, p < 0.001) and had higher echocardiographic scores (8.6 +/- 2 vs 7.4 +/- 1, p < 0.05). Before PMV, mitral gradient was higher (17 +/- 6 vs 13 +/- 5 mm Hg, p < 0.025) and mitral valve area smaller (0.79 +/- 0.2 vs 0.96 +/- 0.2 cm2, p < 0.005) in group I patients, who also had higher pulmonary vascular resistances (469 +/- 299 vs 157 +/- 125 dynes s-1 cm-5, p < 0.005). On multivariate analysis patients in group I were more symptomatic, had smaller mitral valve areas and higher mitral gradients. PMV success (area gain > 50% without complications) was similar (89 vs 87%) in both groups. After PMV final mitral gradient (5 +/- 2 vs 4 +/- 2 mm Hg) and area (1.82 +/- 0.5 vs 1.87 +/- 0.5 cm2) were similar in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Early and late results of percutaneous mitral valvuloplasty for mitral stenosis associated with mild mitral regurgitation.

To assess the influence of mild mitral regurgitation (MR) on the initial and long-term results of percutaneous mitral valvuloplasty (PMV), the baseline characteristics, early results and follow-up of 102 consecutive patients with mild MR before PMV (group I) were prospectively analyzed and compared with those of 186 consecutive patients without MR (group II). Age, gender and symptomatic status were similar in both groups, but more patients in group I were in atrial fibrillation (70 vs 54%, p < 0.05) and had had a previous episode of pulmonary edema (25 vs 14%, p < 0.05). On echocardiography, patients in group I had larger left atria (58 +/- 12 vs 53 +/- 10 mm, p < 0.05) and more calcified mitral valves (score 1.9 +/- 0.8 vs 1.5 +/- 0.7, p < 0.05), but the total echocardiographic score (8.0 +/- 2 vs 7.3 +/- 2) was similar in both groups. Baseline hemodynamic data were also similar in both groups. On multivariate analysis, group I patients were only independently associated with more calcified mitral valves and larger left atria. PMV success (area gain > or = 50% without complications) was similar (88 vs 86%) in both groups, but mitral valve area gain was smaller (0.8 +/- 0.3 vs 1.0 +/- 0.3 cm2, p < 0.05) in group I. After PMV an increase in the severity of MR > or = 2 grades (17 vs 6%, p < 0.05) occurred more frequently in group II patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1993

A variable DNA region of Entamoeba histolytica is expressed in several transcripts which differ in genetically related clones.

A highly variable DNA region (EhVR1), isolated from Entamoeba histolytica clone A, strain HM1:IMSS, is transcribed into several transcripts, which differ in genetically related clones. EhVR1 (3.5 kb) is composed of two contiguous fragments; one of these 1.9 kb long, at the 3' end, identified similar transcripts in clones A, L6 and C2 (all derived from strain HM1:IMMS), the other of 1.6 kb, at the 5' end, detected 0.5, 0.6 and 0.7 kb transcripts only in clone A. Variability of the 1.6 kb fragment was found even within the same clone maintained under different conditions. EhVR1 was localized to 1.3 and 1.4 Mb linear chromosomes and also found in circular molecules. The sequence of the 1.6 kb fragment revealed the presence of a large number of different repeats, including inverted and palindromic repeats. A p145 sequence, previously detected in episomal DNA of the amoeba, was found at the 5' end of EhVR1. The presence of EhVR1 in linear and circular molecules, its high number of repeats, and its variability in genetically related clones suggest the existence of DNA regions that undergo dynamic non-reciprocal recombination between circular episomes and linear chromosomes, and may thus contribute to variability in the trophozoite genome.

Animals↗