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Biomedical subjects

L Garrido

Publications and source records attributed to L Garrido.

At least 19 recordsLinked to original sources
PubMed2000

Isolation and structure elucidation of new cytotoxic steroids from the gorgonian Leptogorgia sarmentosa.

The gorgonian Leptogorgia sarmentosa contains three new steroids, (20S)-20-hydroxycholestane-3,16-dione (1), (16S, 20S)-16,20-dihydroxycholestan-3-one (2), and (20S)-20-hydroxycholest-1-ene-3,16-dione (3) together with a known related compound (4). Their structures were defined by spectroscopic analysis. The new steroids exhibited significant cytotoxicity against four tumor cell lines (ED50 = 1 microg/ml).

Animals↗
PubMed1999

Multinuclear solid-state three-dimensional MRI of bone and synthetic calcium phosphates.

Multinuclear three-dimensional solid-state MRI of bone, tooth, and synthetic calcium phosphates is demonstrated in vitro and in vivo with a projection reconstruction technique based on acquisition of free induction decays in the presence of fixed amplitude magnetic field gradients. Phosphorus-31 solid-state MRI provides direct images of the calcium phosphate constituents of bone substance and is a quantitative measurement of the true volumetric bone mineral density of the bone. Proton solid-state MRI shows the density of bone matrix including its organic constituents, which consist principally of collagen. These solid-state MRI methods promise to yield a biological picture of bone richer in information concerning the bone composition and short range-crystalline order than the fluid-state images provided by conventional proton MRI or the density images produced by radiologic imaging techniques. Three-dimensional solid-state projection reconstruction MRI should be readily adaptable to both human clinical use and nonmedical applications for a variety of solids in materials science.

Bone and Bones↗
PubMed1999

Analysis of periprosthetic capsular tissue from women with silicone breast implants by magic-angle spinning NMR.

The amount of silicone (polydimethylsiloxane [PDMS]) in capsular tissue surgically removed from women with breast implants was measured by using (29)Si and (1)H magic-angle spinning solid-state NMR spectroscopy. Twelve women having smooth surface silicone gel-filled implants, including a subject with "low-bleed" double-lumen implants, had detectable levels of PDMS ranging from 0. 05 to 9.8% silicon in wet tissue (w/w). No silicon-containing compounds other than PDMS were detected. No correlation was found between the amount of PDMS measured in the capsular tissue and the length of implantation time (Pearson correlation coefficient, r = 0. 22). The results showed no relationship between higher amounts of PDMS and capsular contracture (p = 0.74) or other symptoms (p = 0. 53). Magn Reson Med 42:436-441, 1999.

Breast↗
PubMed1999

Response

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Journal Article↗
PubMed1999

Biodegradation of polysiloxanes in lymph nodes of rats measured with 29Si NMR.

Linear and cyclic polysiloxanes and extracts (free polymer) from a silicone gel-filled implant are used to investigate the reactivity of silicones in vivo. Aqueous emulsions of polysiloxanes and controls (without polysiloxanes) are injected once (day 0, approximately 10% w/v) or six times (starting at day 0, every 14 days, approximately 3% w/v) in the right thigh of rats and the popliteal and lumbar lymph nodes are harvested (3 rats per time point and compound investigated) at 2, 16, 30, 44, 58 and 72 days after the injection. 29Si NMR spectroscopy is used to detect and evaluate the presence of polysiloxanes and their metabolites in the lymph nodes. In addition to the resonance associated with the polysiloxane injected (approximately -20 ppm), the NMR spectra of lymph nodes show new resonances that are attributed to partially hydrolyzed polysiloxanes (-5 to -15 ppm) and silica (-90 to - 120 ppm). These resonances are not present in polysiloxanes emulsions before injection or in the lymph nodes of controls. Our results demonstrate that all polysiloxanes and extracts from silicone gel-filled implants are biotransformed in the lymph nodes, but high molecular weight polymer degrades at a slower rate than oligomers.

Animals↗
PubMed1999

[Use of dual-chamber pacemaker. Short and long-term results].

BACKGROUND: Continuous improvement of dual chamber DDD pacemakers, electrode stability and programmed sequential stimulation changed the prognosis of patients implanted with these devices. AIM: To report our experience with the use of dual chamber pacemakers. MATERIAL AND METHODS: One hundred seventy six patients (116 male), aged 13 to 91 years old, who received a dual chamber pacemaker implant, are reported. Patients were followed for a mean of 2.6 years. RESULTS: Indications for DDD pacemaker were complete atrioventricular block in 43%, sick sinus syndrome in 32%, paroxysmal A-V block in 24%. All pacemakers were Siemens-Pacesetter and were provided with an automatic sensing and threshold device. J shaped atrium electrodes were used in 78% of patients and screw-in electrodes in 22%. Post operative complications were displacement of atrial electrode in 8 patients, of ventricular electrode in 6 patients, infection in two patients and a hematoma in one. Chronic parameters, measured after six months, were within expected ranges and allowed a good reprogramming of pacemakers. Long term programming aimed to reduce battery depletion, enhance device performance and improve hemodynamic conditions. Normal sequential stimulation was achieved in 154 patients (87%), 14 (85) patients died of cardiovascular disease not related to pacemaker function. Eight patients were in atrial fibrillation and were reprogrammed to VVI and DDI modes. CONCLUSIONS: DDD pacemakers are reliable and afford symptomatic relief in a broad spectrum of patients.

Adolescent↗
PubMed1999

[Long-term results of reconstructive surgery for mitral insufficiency].

BACKGROUND: Surgical repair is the procedure of choice for mitral insufficiency since it preserves better left ventricular structure and function. AIM: To assess the long term clinical and echocardiographic results of mitral valve reconstructive surgery. MATERIAL AND METHODS: A review of clinical and echocardiographic data of 68 patients (34 male, age range 17 to 82 years), subjected to surgical mitral valve repair between December 1991 and March 1998. Preoperative functional capacity of these patients was 2.96 +/- 0.7. Surgical repair was assessed using transesophagic echocardiography in all subjects. RESULTS: The etiology of mitral insufficiency was degenerative in 43 patients, rheumatic in 10, infectious in 6, ischemic in 5 and miscellaneous in 4. The most frequent pathological findings were dilatation of the mitral ring in 42% of patients, chordae tendinae rupture in 32% and enlargement in 24%. A mitral anuloplasty was done in 90% of patients, a cuadrilateral resection of posterior leaflet in 52% and chordae tendinae transference in 12%. An additional surgical procedure was done in 34% of subjects. Three patients died during hospitalization (4.4%). During the follow up of 36.5 +/- 22.3 months, five patients died and one required a mitral valve replacement. The actuarial survival probability was 95.3 +/- 2.6% at one year and 83.5 +/- 6.5% at five years. The reoperation free survival was 100% at one year and 97.4 +/- 2.5% at five years. At the end of follow up the functional capacity improved to 1.25 +/- 0.4. Echocardiography showed absence of mitral insufficiency in 48.4% of patients, minimal, mild and moderate insufficiency in 35.5, 14.5 and 1.6% of patients respectively. CONCLUSIONS: Surgical valve reconstruction in mitral insufficiency has satisfactory long term results and should be the procedure of choice for eligible patients.

Adolescent↗
PubMed1998

Determination of right ventricular structure and function in normoxic and hypoxic mice: a transesophageal echocardiographic study.

BACKGROUND: Noninvasive cardiac evaluation is of great importance in transgenic mice. Transthoracic echocardiography can visualize the left ventricle well but has not been as successful for the right ventricle (RV). We developed a method of transesophageal echocardiography (TEE) to evaluate murine RV size and function. METHODS AND RESULTS: Normoxic and chronically hypoxic mice (F(IO2)=0.11, 3 weeks) and agarose RV casts were scanned with a rotating 3.5F/30-MHz intravascular ultrasound probe. In vivo, the probe was inserted in the mouse esophagus and withdrawn to obtain contiguous horizontal planes at 1-mm intervals. In vitro, the probe was withdrawn along the left ventricular posterior wall of excised hearts. The borders of the RV were traced on each plane, allowing calculation of diastolic and systolic volumes, RV mass, RV ejection fraction, stroke volume, and cardiac output. RV wall thickness was measured. Echo volumes obtained in vitro were compared with cast volumes. Echo-derived cardiac output was compared with measurements of an ascending aortic Doppler flow probe. Echo-derived RV free wall mass was compared with true RV free wall weight. There was excellent agreement between cast and TEE volumes (y=0.82x+6.03, r=0.88, P<0.01) and flow-probe and echo cardiac output (y=1.00x+0.45, r=0.99, P<0.0001). Although echo-derived RV mass and wall thickness were well correlated with true RV weight, echo-derived RV mass underestimated true weight (y=0.53x+2.29, r=0.81, P<0.0001). RV mass and wall thickness were greater in hypoxic mice than in normoxic mice (0.78+/-0.19 versus 0.51+/-0.14 mg/g, P<0.03, 0.50+/-0.03 versus 0.38+/-0.03 mm, P<0.04). CONCLUSIONS: TEE with an intravascular ultrasound catheter is a simple, accurate, and reproducible method to study RV size and function in mice.

Animals↗
PubMed1997

Dynamic liver imaging with iron oxide agents: effects of size and biodistribution on contrast.

In vivo effective relaxation rates in normal rat liver were evaluated for four dextran coated iron oxide agents: monocrystalline iron oxide nanocolloid (MION) with a mean particle diameter of 3.9 nm, a polycrystalline agent (PION) with a larger mean diameter of 12 nm, and these two agents labeled with the asialofetuin (ASF) protein for high hepatocytic receptor binding affinity (MION-ASF and PION-ASF). Using echo planar imaging at 2 Tesla, dose response was measured with measured with high temporal resolution for 3 h after injection of agent, and by comparing with relaxivities in vitro and in brain, dominant in vivo contrast phenomena were elucidated. While transverse relaxivity for PION-ASF exceeded that for MION-ASF by almost a factor of 2 in solution, relaxation rates in vivo became equivalent. Liver relaxation using non-ASF agents was consistent with rapid water exchange between vascular and extravascular compartments, which dominated relaxation as a result of agent accumulation in Kupffer cells.

Animals↗
PubMed1997

[Pulmonary alveolar proteinosis: ultrastructural study of 4 cases].

Pulmonary Alveolar Proteinosis (PAP) is a rare and diffuse lung disease characterized by the abnormal deposition of PAS positive, lipoproteinaceous material in the alveolar spaces. It has been related, mainly, to alterations in the immune state and to secondary infections. We studied four cases of PAP diagnosed by light microscopy. In two cases we were able to demonstrate disseminated Histoplasmosis related to immunodeficiency states (AIDS and malnutrition), one case with Pneumocystis carinii infection and AIDS, and one case with no related pathology. Granular and electron dense material, concentric myelin figures, and variable-sized osmiophilic bodies were observed by electron microscopy. We found yeast-like structures, trophozoites and cysts in the alveolar spaces, in the Histoplasmosis and Pneumocystic carinii infection cases, respectively. In one of our cases, the circulating neutrophils showed crystalloid inclusions in the nucleus. PAP should be considered in the differential diagnoses of patients with pulmonary infiltrates.

Adult↗
PubMed1997

[24 hour esophageal pH monitoring in healthy individuals].

BACKGROUND: Twenty four hour esophageal pH monitoring is considered the gold standard investigation for gastroesophageal reflux disease. This test allows the linkage of symptoms to occurrence of reflux episodes and is used to record the frequency of reflux and the amount of esophageal acid exposure that results from reflux. AIM: To know the acid esophageal exposure in healthy Chilean subjects. SUBJECTS AND METHODS: Thirty two asymptomatic volunteers aged 30 to 76 years old (24 female) underwent 24 h esophageal pH monitoring with a digitrapper Mark II Gold (Synectics Medical Stockholm). Total reflux episodes, episodes greater than 5 min, the longest reflux episode, the lapse with pH < 5, the percentage of time with pH < 4 and the score suggested by Johnson and De Mester were analyzed. RESULTS: There was a mean of 20.9 reflux episodes per subject and 0.1 episodes of more than 5 min. The longest episode lasted 8 min and the mean total time of acid reflux was 10 min/24 h. Total percentage pH below 4 was 0.7% and the mean score was 3.2. No subject reported symptoms during the test. CONCLUSIONS: For practical purposes, the upper limit of normal acid exposure in Chilean subjects is 2.4%.

Adult↗
PubMed1996

Enhanced resolution of proton NMR spectra of malignant lymph nodes using magic-angle spinning.

Proton NMR spectroscopy has proven useful in the detection of cancer in lymph node tissue. However, due to the high fat content of this type of tissue, 2D 1H COSY measurements (requiring acquisition times of 4-5 h or longer) are necessary to obtain the spectral information necessary for diagnosis. T2-filtered proton magic-angle spinning (MAS) NMR spectroscopy provides 1D spectra of lymph nodes in approximately 20 min with sufficient spectral resolution allowing for identification of changes in cellular chemistry due to the presence of malignant cells. MAS data from lymph nodes of five control and six rats with mammary adenocarcinoma (R13762) demonstrated increases in the signal intensity of resonances associated primarily with lactate (delta = 4.12 ppm) P < 0.0004, creatines/lysine (delta = 3.04 ppm) P < 0.0032, and glutamate/ glutamine (delta = 2.36 ppm) P < 0.0002 in metastatic compared with normal lymph nodes. The infiltration of lymph nodes by malignant cells is an important prognostic factor for many cancers. The rapid assessment of node tissue without the introduction of sampling errors (inherent in currently employed histological procedures) would allow postoperative therapy decisions to be made more efficiently.

Adenocarcinoma↗
PubMed1996

Analytical interpretation of feed-forward nets outputs after training.

The minimization quadratic error criterion which gives rise to the back-propagation algorithm is studied using functional analysis techniques. With them, we recover easily the well-known statistical result which states that the searched global minimum is a function which assigns, to each input pattern, the expected value of its corresponding output patterns. Its application to classification tasks shows that only certain output class representations can be used to obtain the optimal Bayesian decision rule. Finally, our method permits the study of other error criterions, finding out, for instance, that absolute value errors lead to medians instead of mean values.

Algorithms↗
PubMed1996

Silicone gel-filled breast implants in women: findings at H-1 MR spectroscopy.

PURPOSE: To evaluate, at hydrogen-1 magnetic resonance (MR) spectroscopy, the effect of implantation time, implant status, and implant removal on the amount of silicone in the liver in women with silicone gel-filled breast prostheses. MATERIALS AND METHODS: The study population included 55 women (39 patients with silicone gel-filled prostheses and seven from whom implants had been removed, and nine control subjects [eight with no implant and one with saline-filled implants]). Stimulated-echo acquisition mode, or STEAM, H-1 MR spectroscopy was performed to determine the concentration of silicone in the liver. Implant status at the time of spectroscopy was diagnosed at MR imaging. RESULTS: Twenty of 39 (51%) women with implants had ruptured prostheses. Resonances associated with the presence of silicone and partially hydrolyzed silicone (0.3 to -0.8 ppm with respect to water at 4.7 ppm) and other resonances that are not yet assigned (-2 to -5 ppm) were detected in 27 (69%) of the 39 women (17 with ruptured implants). Relative signal intensities of the silicone species detected in the liver in these women were found to vary substantially and were not correlated with the status of the implants (P > .70). Silicone resonances were not detected in the livers in the nine control subjects. After implant removal, no resonances between 0.3 and -0.8 ppm were observed in six of seven women, but silicone-related peaks were still detectable in the region of -2 to -5 ppm. CONCLUSION: Proton MR spectra obtained in the liver of women with silicone gel-filled breast implants helped measure silicone exposure.

Adult↗