Biomedical subjects

H Garcia

Publications and source records attributed to H Garcia.

At least 19 recordsLinked to original sources

PubMed2006

Isotope effect on the thermal conductivity of boron nitride nanotubes.

We have measured the temperature-dependent thermal conductivity kappa(T) of individual multiwall boron nitride nanotubes using a microfabricated test fixture that allows direct transmission electron microscopy characterization of the tube being measured. kappa(T) is exceptionally sensitive to isotopic substitution, with a 50% enhancement in kappa(T) resulting for boron nitride nanotubes with 99.5% 11B. For isotopically pure boron nitride nanotubes, kappa rivals that of carbon nanotubes of similar diameter.

Journal Article↗

PubMed2005

The detection and PCR-based characterization of the parasites causing trypanosomiasis in water-buffalo herds in Venezuela.

The usefulness of PCR-based assays for detecting trypanosomiasis in water buffaloes and other livestock was explored, under field conditions, in Venezuela. The sensitivity and specificity of the assays, which were based on established primer pairs (21-mer/22-mer and ILO1264/ILO1265), were evaluated, partly by comparison with the results of parasitological tests (stained bloodsmears and microhaematocrit centrifugation) and immunological assays (IFAT) run in parallel. The optimised PCR-based assays showed a sensitivity of 10 pg DNA. The use of the 21-mer/22-mer primer pair gave a test that was specific for species in the subgenus Trypanozoon (including Trypanosoma evansi), whereas use of ILO1264/ILO1265 produced a test that was specific for T. vivax. The results of a hybridization assay using T. evansi-DNA and T. vivax-DNA probes indicated no cross-hybridization between the T. evansi and T. vivax PCR products.The results of the bloodsmear examinations, microhaematocrit centrifugations (MHC) and IFAT indicated that 23 (6.7%), 39 (11.4%) and 135 (39.5%) of the 342 blood samples investigated (including 316 from water buffaloes) contained trypanosomes, respectively. The results of the PCR-based assays indicated that 68 (19.9%) of the same blood samples contained T. vivax (or at least T. vivax DNA), and that none contained T. evansi or any other member of the subgenus Trypanozoon. For the detection of trypanosomes, the assay therefore appeared almost twice as sensitive as the MHC. These results are the first on the molecular characterization of the trypanosomes infecting water buffaloes in Venezuela. When the results of the MHC (which is the most practical, and frequently used, alternative detection method) were used as the gold standard, the PCR-based assay for T. vivax was found to have 100% sensitivity, 90.4% specificity, a positive predictive value of 0.57, a positive likelihood ratio of 10.45, and a negative likelihood ratio of 0.00. The assay therefore appears a reasonable choice for detecting T. vivax in the mammalian livestock of Venezuela and elsewhere.

Animals↗

PubMed2004

Augmentation mammoplasty and "silicone-osis".

BACKGROUND: Claims have been made that breast augmentation induces a previously unrecognized disease ("silicone-osis"). AIMS: To confirm the existence of "silicone-osis", qualify and quantify its characteristics. METHODS: In this population-based retrospective cohort study, the health status of 458 female Sydney residents who had augmentation mammoplasty for cosmetic reasons ("augmentation mammoplasty-exposed" or "exposed" cohort) between 1979 and 1983 was compared with the health status of 687 female Sydney residents who had non-silicone-associated plastic surgery ("augmentation mammoplasty-nonexposed" or "non-exposed" cohort). Both groups were matched for age (+/- 5 years), year of plastic surgery (+/- 2 years), plastic surgeon, anaesthetist and mode of anaesthesia. Outcome measures comprised dummy symptoms to assess reporting bias, as well as symptoms and symptom clusters from a comprehensive 78-symptom list. RESULTS: Dummy variables were not over-reported by the exposed cohort. The following individual symptoms developed more commonly in the exposed cohort after index plastic surgery: "memory loss/confusion", "altered bowel habit", "chest pain made worse by deep breathing", "shortness of breath after walking up 10 steps", "breast pain", "sweating mainly at night" and "tunnel vision". Of eight identified symptom clusters, three were rejected as biologically unimportant: "joint swelling of the bunion joint", "haemorrhoids" and "breast lumps" (the latter two occurring more commonly in the non-exposed cohort). In contrast, five symptom clusters were thought to have potential biological importance and occurred more commonly in the exposed cohort. The symptom "night sweats" was common to all five clusters, and comprised the sole symptom in one instance. The other four multisymptom clusters were also characterized by "low energy" (lethargy) and "pins and needles", whereas "breast pain", "impaired memory", "muscle pain" and "reflux", occurred in three of the four clusters. CONCLUSION: Cluster analysis suggested the existence of a multisystem disorder occurring more commonly in the exposed cohort and characterized by night sweats, lethargy, breast pain, impaired mentation, reflux, paraesthesiae, hand muscle weakness and myalgia. The argument against this being a new disease entity --"silicone-osis"-- however, was its presence, albeit at lower frequency, in the silicone-unexposed cohort. Thus this study did not confirm the existence of a new disease entity "silicone-osis" uniquely and causally associated with silicone exposure. The possible interpretations of these findings are discussed.

Autoimmune Diseases↗

PubMed2003

Single-trial event-related potentials with wavelet denoising.

The application of a recently proposed denoising implementation for obtaining event-related potentials (ERPs) at the single-trial level is shown. We study its performance in simulated data as well as in visual and auditory ERPs. For the simulated data, the method gives a significantly better reconstruction of the single-trial event-related responses in comparison with the original data and also in comparison with a reconstruction based on conventional Wiener filtering. Moreover, with wavelet denoising we obtain a significantly better estimation of the amplitudes and latencies of the simulated ERPs. For the real data, the method clearly improves the visualization of both visual and auditory single-trial ERPs. This allows the calculation of better averages as well as the study of systematic or unsystematic variations between trials. Since the method is fast and parameter free, it could complement the conventional analysis of ERPs.

Artifacts↗

PubMed2002

High blood pressure and decreased heart rate variability in the Cuban epidemic neuropathy.

Autonomic cardiovascular reflexes were investigated in patients with an epidemic optic and peripheral neuropathy, which affected more than 50 000 people in Cuba between 1991 and 1994 and was probably caused by nutritional deficiency. Affected patients had significantly higher blood pressure than age matched controls, both while supine and standing, and significantly lower heart rate variability during paced breathing, suggesting reduced cardiac parasympathetic innervation.

Adult↗

PubMed2002

Frequency evolution during tonic-clonic seizures.

By using the Short Time Fourier Transform, we analyzed the EEG frequency evolution during tonic-clonic seizures on 18 scalp recordings corresponding to 7 patients admitted for Video-EEG monitoring. This information was correlated with clinical findings observed in the video recordings. From the time-frequency plots, we recognized patterns related with brain activity even when embedded in a background of muscle artifacts. In 13/18 seizures we found a clear frequency dynamics characterized by an activity originally localized at about 8 Hz, later slowing down to about 1.5 Hz. In the remaining cases muscle artifacts hinder the disclosure of a clear frequency evolution. The clonic phases started when the main frequency slowed down to about 3 Hz. We conclude that the Short Time Fourier Transform is very useful for a quantitative analysis of epileptic seizures, especially when muscle artifacts contaminate the recordings. We further conclude that the clonic phase starts as a response to brain activity that can be only established when brain oscillations are slow enough to be followed by the muscles.

Adult↗

PubMed2001

Dynamics of nonstructural carbohydrates and biomass yield in a fodder legume tree at different harvest intensities.

Tropical tree fodder is harvested by frequent prunings, and resprouting depends on nonstructural carbohydrate reserves in the remaining tree parts. We studied the effects of three pruning intensities (removal of all leaves and branches leaving 1 m of stem once a year (T-12), or every 6 months (T-6), and about 50% pruning every 2 months (P-2)) on regrowth and the dynamics of soluble sugars and starch in the legume tree Gliricidia sepium (Jacq.) Walp. growing under humid tropical conditions in Guadeloupe, Lesser Antilles. Carbohydrates were sampled in roots, stems and branches. Among pruned trees, trees in the T-6 harvest regime had the highest leaf fodder yield (0.73 kg tree(-1) year(-1)). High litter loss reduced leaf yield of T-12 trees, but compared with the other treatments, T-12 trees produced the most branch biomass (3.43 kg tree(-1)). Among treatments, P-2 trees had an intermediate leaf fodder yield and the lowest branch production. Sucrose, glucose and fructose were the most common sugars in all biomass compartments. Mannose, pinitol and an unidentified cyclitol were relatively abundant in branches. Root sugar and starch concentrations were unaffected by harvest regime. There was a significant interactive effect of harvest intensity and regrowth time on stem sugar concentration. Stem starch concentration was highest in T-12 trees. After a year of fodder harvesting, whole-tree reserves of nonstructural carbohydrates were highest in T-12 trees; however, a larger proportion of reserves were located in roots and stems of T-6 and P-2 trees. These reserves, which were not lost in pruning and contributed to regrowth of G. sepium after pruning, may explain the relatively small effects of harvesting regime on soluble sugar and starch concentrations.

Biomass↗

PubMed2000

UV-vis and IR spectral characterization of persistent carbenium ions, generated upon incorporation of cinnamyl alcohols in the acid zeolites HZSM-5 and HMor

Cinnamyl alcohol (1) and two derivatives 2 and 3 have been incorporated in dehydrated HMor and HZSM-5 zeolites with the aim to characterize spectroscopically the corresponding carbocations generated within the solids. Product studies of the supernatant liquid phase combined with diffuse reflectance UV-vis and IR spectroscopy provide unequivocal evidence for the carbocations. Thus, cinnamyl alcohol (1) affords the 1,5-diphenylpentadienyl cation in HMor and HZSM-5 as a persistent species. In the case of HMor with larger pore dimensions the bulkier 1-(2'-cinnamyl)-3-phenylpropenyl cation was also spectroscopically detected. No persistent carbocation was observed when the alpha-methylcinnamyl alcohol (2) was incorporated in the acid zeolites, wherein a complete cyclization to 2-methylindene takes place. Finally, incorporation of 2-methyl-4-tolyl-3-buten-2-ol (3) in HZSM-5 allowed detection of the gem-dimethyl-subsituted p-methylcinnamyl cation, with a lifetime of hours. This cation is not persistent enough in HMor to be characterized. The present study illustrates how structurally related allylic substrates may give distinct carbenium ions whose persistence depends on the host-guest fit in the interior of the acid zeolites.

Journal Article↗

PubMed2000

Primary cardiac lymphoma diagnosed by percutaneous intracardiac biopsy with combined fluoroscopic and transesophageal echocardiographic imaging.

Primary cardiac tumors have very low prevalence with cardiac lymphoma, being one of the rarest forms. Several recent reports have shown transesophageal echocardiography to be an accurate technique for characterizing and localizing these neoplasms, with results comparable to CT and MRI scans. Transvenous intracardiac tumor biopsy has been employed as a minimally invasive technique to obtain tissue samples. The addition of transesophageal echocardiographic (TEE) guidance to this process has increased the accuracy of obtaining diagnostic specimens while improving patient safety. We review published cases of this relatively new technique using combined fluoroscopic and TEE guidance and present a case of primary cardiac lymphoma diagnosed by this method. The patient achieved complete tumor remission after treatment with standard chemotherapy and remains fully functional 32 months after initial diagnosis.

Aged↗

PubMed2000

Meteorological factors affecting daily urticaceae pollen counts in southwest Spain.

The influence of meteorological factors on daily Urticaceae pollen counts were studied in Córdoba (southwest Spain) in 1996 and 1997. The daily Urticaceae pollen concentrations were obtained by using a Hirst-type volumetric sampler, and meteorological data were obtained from the Córdoba airport, located near the sampling site. The highest correlation between pollen concentration and meteorological parameters was obtained during non-rainy seasons. Temperature was found to be the most important meteorological parameter influencing pollen counts in spring, as temperature is the main reason for the increase of pollen concentration in the atmosphere. In autumn, humidity was another important parameter influencing pollen counts. Rain, however, did not appear to be significant. The influence of the pollen concentration of the 2 previous days and the pollen concentration of the previous day has been studied. During periods with low precipitation, the pollen concentration of the previous day was a useful predictor of Urticaceae pollen concentrations for the following day.

Climate↗

PubMed2000

Both dermal matrix and epidermis contribute to an inhibition of wound contraction.

Contracture is a major detriment to functional recovery from large wounds. To determine the relative value of dermal replacement and epidermal coverage in inhibiting wound contraction, five full-thickness wounds (all 5 x 5 cm2) were placed on the back of 8 swine and treated in the following manner: (1) open wound, (2) porcine acellular dermis (analogous to AlloDerm for human use), (3) porcine acellular dermis with epidermal autograft placed 7 days postwounding, (4) porcine acellular dermis with immediate epidermal autograft, and (5) conventional-thickness autograft. Scar dimensions and punch biopsies were taken at days 14 and 30 postwounding. The planimetry results demonstrated that wound contraction was significantly greater with the open wounds (group 1) than all other wounds with a dermal substitute. Furthermore, wounds with initial epidermal coverage had significantly less contraction than unepithelialized wounds (14.8 +/- 1.1 cm2 at day 14 in wound group 2 vs. 20.4 +/- 0.6 cm2 in wound group 4; p < 0.05). Biopsy results revealed that wounds with initial epithelial coverage had the least amount of inflammation. These findings suggest that both dermal matrix and epidermal coverage contribute to an inhibition of wound contraction and that prompt epithelial coverage appears to impede contraction by reducing inflammation.

Animals↗

PubMed2000

A proposal to declare neurocysticercosis an international reportable disease.

Neurocysticercosis is an infection of the nervous system caused by Taenia solium. It is the most important human parasitic neurological disease and a common cause of epilepsy in Africa, Asia, and Latin America, representing enormous costs for anticonvulsants, medical resources and lost production. Neurocysticercosis is a human-to-human infection, acquired by the faecal-enteric route from carriers of intestinal T. solium, most often in areas with deficient sanitation. Intestinal tapeworms cause few symptoms, but adult taeniae carried by humans release large numbers of infective eggs and are extremely contagious. Ingestion of poorly cooked pig meat infested with T. solium larvae results in intestinal taeniosis but not neurocysticercosis. With a view to hastening the control of taeniosis and neurocysticercosis we propose that neurocysticercosis be declared an international reportable disease. New cases of neurocysticercosis should be reported by physicians or hospital administrators to their health ministries. An epidemiological intervention could then be launched to interrupt the chain of transmission by: (1) searching for, treating and reporting the sources of contagion, i.e. human carriers of tapeworms; (2) identifying and treating other exposed contacts; (3) providing health education on parasite transmission and improvement of hygiene and sanitary conditions; and (4) enforcing meat inspection policies and limiting the animal reservoir by treatment of pigs. We believe that the first step required to solve the problem of neurocysticercosis is to implement appropriate surveillance mechanisms under the responsibility of ministries of health. Compulsory notification also has the major advantage of providing accurate quantification of the incidence and prevalence of neurocysticercosis at regional level, thus permitting the rational use of resources in eradication campaigns.

Adolescent↗

PubMed1999

Change from conventional haemodiafiltration to on-line haemodiafiltration.

BACKGROUND: On-line haemodiafiltration (HDF) is a technique which combines diffusion with elevated convection and uses pyrogen-free dialysate as a replacement fluid. The purpose of this study was to evaluate the difference between conventional HDF (1-3 l/h) and on-line HDF (6-12 l/h). METHODS: The study included 37 patients, 25 males and 12 females. The mean age was 56.5 +/- 13 years and duration of dialysis was 62.7 +/- 49 months. Three patients dropped out for transplantation, three patients died and three failed to complete the study period. Initially all patients were on conventional HDF with high-flux membranes over the preceding 34 +/- 32 months. Treatment was performed with blood flow (QB) 402 +/- 41 ml/min, dialysis time (Td) 187 min, dialysate flow (QD) 654 +/- 126 ml/min and replacement fluid (Qi) 4.0 +/- 2 l/session. Patients were changed to on-line HDF with the same filtre and dialysis time, QD 679 +/- 38 ml/min (NS), QB 434 +/- 68 ml/min (P < 0.05) and post-dilutional replacement fluid 22.5 +/- 4.3 l/session (P < 0.001). We compared conventional HDF with on-line HDF over a period of 1 year. Dialysis adequacy was monitored according to standard clinical and biochemical criteria. Kinetic analysis of urea and beta2-micro-globulin (beta2m) was performed monthly. RESULTS: Tolerance was excellent and no pyrogenic reactions were observed. Pre-dialysis sodium increased 2 mEq/l during on-line HDF. Plasma potassium, pre- and post-dialysis bicarbonate, uric acid, phosphate, calcium, iPTH, albumin, total proteins, cholesterol and triglycerides remained stable. The mean plasma beta2m reduction ratio increased from 56.1 +/- 8.7% in conventional HDF to 71.1 +/- 9.1% in on-line HDF (P < 0.001). The pre-dialysis plasma beta2m decreased from 27.4 +/- 8.1 to 24.2 +/- 6.5 mg/l (P < 0.01). Mean Kt/V (Daugirdas 2nd generation) was 1.35 +/- 0.21 in conventional HDF compared with 1.56 +/- 0.29 in on-line HDF (P < 0.01), Kt/Vr (Kt/V taking into consideration post-dialysis urea rebound) 1.12 +/- 0.17 vs 1.26 +/- 0.20 (P < 0.01), BUN time average concentration (TAC) 44.4 +/- 9 vs 40.6 +/- 10 mg/dl (P < 0.05) and protein catabolic rate (PCR) 1.13 +/- 0.22 vs 1.13 +/- 0.24 g/kg (NS). There was a significant increase in haemoglobin (10.66 +/- 1.1 vs 11.4 +/- 1.5) and haematocrit (32.2 +/- 2.9 vs 34.0 +/- 4.4%), P < 0.05, during the on-line HDF period, which allowed a decrease in the erythropoietin doses (3861 +/- 2446 vs 3232 +/- 2492 UI/week), (P < 0.05). Better blood pressure control (MAP 103.8 +/- 15 vs 97.8 +/- 11 mmHg, P < 0.01) and a lower percentage of patients requiring antihypertensive drugs were also observed. CONCLUSION: The change from conventional HDF to on-line HDF results in increased convective removal and fluid replacement (18 l/session). During on-line HDF treatment, dialysis dose was increased for both small and large molecules with a decrease in uraemic toxicity level (TAC). On-line HDF provided a better correction of anaemia with lower dosages of erythropoietin. Finally, blood pressure was easily controlled.

Adult↗

PubMed1999

Pulmonary artery fibrous bands: report of a case with extensive lung infarction and superinfection with Coccidioides immitis, Pseudomonas, and acid-fast bacilli.

A 46-year-old woman presented with shortness of breath and frequent lower respiratory tract infections. A ventilation-perfusion scan showed markedly reduced perfusion of the right lung, and pulmonary arteriogram showed stenosis of the right pulmonary artery. A right pneumonectomy revealed dense white fibrous bands partially occluding the pulmonary artery branches and two large abscess cavities filled with pus in the upper and lower lobes. Microscopic examination revealed extensive necrosis of lung parenchyma, suppurative granulomatous inflammation with Coccidioides immitis organisms and rare acid-fast bacilli. Pulmonary artery fibrous bands were originally believed to be congenital; however, they are now known to be sequelae of thromboembolic phenomena.

Coccidioides↗

PubMed1998

Evaluation of peri- and post-natal toxicity of Policosanol in rats.

The effects of Policosanol, a newly developmented hypocholesterolemic drug administered during the perinatal and postnatal periods, were studied in Sprague-Dawley rats. This compound was administered orally to female rats at dose levels of 0 (control), 5, 50, and 500 mg/kg/day, from day 15 of pregnancy to day 21 after parturition. The animals were allowed to deliver and their offspring were examined for postnatal growth and development. No signs of toxic effects related to the test material were observed in the dams F0 during pregnancy and lactation. No adverse effects were observed on the postnatal growth, behaviours, or reproductive ability of pups F1. The physical and sensorial development of pups F2 was also normal. These results confirm that Policosanol does not affect the reproductive performance or fetal/neonatal development.

Animals↗

PubMed1998

Urea reduction ratio considering urea rebound.

An American National Study shows that survival benefits from higher dialysis doses appear to be present up to a Kt/V level of 1.3 or a urea reduction ratio (URR) of 70%. The effect of increasing dialysis efficiency magnified urea rebound and the error in URR determinations. Several formulas have been developed to calculate URR considering the urea rebound (URRr). Smye and coworkers have proposed a method whereby the equilibrated blood urea nitrogen is predicted by additional intradialytic urea sample. Maduell and colleagues, based on analysis of postdialysis urea rebound, have proposed a method whereby the urea rebound is predicted. To compare measured URRr to estimated by Smye and Maduell formulas, 384 patients were studied, 211 males and 173 females, who received a dialysis session with their habitual parameters. Measurements of plasma urea concentration were obtained at the beginning, 90-100 min following the start of dialysis, at the end, and 45 min after dialysis. The postdialysis urea rebound was 22.4+/-9.7%. The urea kinetic model Kt/V was 1.365+/-0.26, and Kt/Vr was 1.14+/-0.23. URR was 68.7+/-6.6%, and when it was calculated with urea rebound, it decreased to 61.9+/-7.4%. The URRr correlated with calculations by Smye and Maduell formulas: 60.7+/-8.4 (r = 0.722, p < 0.001) and 61.8+/-6.6 (r = 0.933, p < 0.001), respectively. The precision of estimated limits of agreement and percentage of error by Bland and Altman analysis show that URRr estimated Maduell formula could be used in place of the URRr. Otherwise, the degree of agreement of the Smye method was not clinically acceptable. In conclusion, our results led us to suggest that in actual dialysis, the use of URR is not adequate for delivered hemodialysis dose, and URRr should be used. URRr estimated by Maduell formula could be a simple and accurate method for use in clinical practice. The recommended dialysis dose by the American National Study of URR of 70% could correspond, considering urea rebound, to Kt/Vr 1.18 or URRr of 64%.

Adult↗

PubMed1997

Searching for hidden information with Gabor Transform in generalized tonic-clonic seizures.

The analysis of generalized tonic clonic seizures is usually difficult with scalp EEG due to muscle artifact. We applied Gabor Transform to evaluate 20 seizures from 8 consecutive patients admitted for video-EEG monitoring. We studied the relative intensity ratios of alpha, theta and delta bands over time. In 14/20 events we found a significant decremental activity in the delta band at the onset of the seizure indicating that this is dominated by theta and alpha bands. We conclude that GT is a useful auxiliary tool in the analysis of ictal activity that sheds light on the underlying pathophysiological mechanisms.

Adult↗

PubMed1997

Validation of different methods to calculate Kt/V considering postdialysis rebound.

BACKGROUND: The effect of increasing dialysis efficiency magnifies rebound urea and the error in Kt/V determinations from single pool urea kinetics. Several formulae have been developed to calculate Kt/V taking into account the rebound urea (Kt/Vr). Smye et al. proposed a method whereby the equilibrated BUN is predicted by an additional intradialytic urea sample (Kt/VrSmye). Daugirdas et al. proposed a method where a single pool Kt/V is modified according to the speed of dialysis to obtain a double pool Kt/V (Kt/VrDaug). Maduell et al. developed a method based on analysis of post-dialysis urea rebound whereby the Kt/Vr is predicted according to the single pool Kt/V and K/V (Kt/VrMad). DESIGN OF THE STUDY: We compared Kt/Vr estimated by these three formulae (Smye, Daugirdas, and Maduell) in 384 patients consisting of 211 males and 173 females, who received dialysis according to their regular protocols. Plasma urea was measured at the beginning, 90-100 min following the start of dialysis, the end, and 45 min post-dialysis. RESULTS: Post-dialysis rebound urea was 22.4 +/- 9.7%. Kt/V and Kt/Vr obtained with rea kinetic model Kt/V 1.184 +/- 0.22 and 0.984 +/- 0.20, respectively. These was a good correlation between Kt/Vr and the Smye formula (Kt/VrSmye = 0.956 +/- 0.21, r = 0.729, P < 0.001), and a better one for Daugirdas (Kt/VrDaug = 0.984 +/- 0.18, r = 0.931, P < 0.001), and Maduell formulae (Kt/VrMad = 0.980 +/- 0.18, r = 0.946, P < 0.001). Limits of agreement and percentage of error estimated according to Bland and Altman show that Kt/Vr estimated by Daugirdas and Maduell formulae could be used in place of the Kt/Vr. The degree of agreement with the Smye method is not clinically acceptable. CONCLUSION: Our results suggest that the use of a single pool Kt/V is not adequate to estimate the haemodialysis dose delivered and Kt/V taking rebound urea in consideration. Kt/Vr estimated by Daugirdas or Maduell formulae are a simple and accurate method for use in clinical practice.

Adult↗