Search PubMed⌕ Search

Biomedical subjects

A Varela

Publications and source records attributed to A Varela.

At least 73 records · Page 4Linked to original sources
PubMed1997

Effects of 3-hydroxybutyrate on the hypoxic and reoxygenated atria from fed and fasted rats.

When exposed to hypoxia, the isolated atria from fed rats released lactate into the medium and underwent a decline of the peak developed tension and pacemaker frequency. The atria from 24-h fasted rats showed a rise in the resting tension together with a greater decline of the pacemaker rate and a lower lactate output than those from fed rats. The exposure to 5 mM 3-hydroxybutyrate caused only a small and brief decline in the pacemaker rate in the fed rats atria indicating that ketone bodies are able to exert only a minor detrimental effect on the hypoxic atria. Since the lactate output remained unaffected, this effect cannot be ascribed to a lowering in the energy supply from anaerobic glycolysis. On the contrary, 3-hydroxybutyrate improved the post-hypoxic recovery of the peak tension in the atria from fasted rats. This finding may be reflecting an anaplerotic role of 3-hydroxybutyrate, thus suggesting that in addition to glucose a second substrate is needed to meet the energy demand in the reoxygenated atria from fasted rats.

3-Hydroxybutyric Acid↗
PubMed1996

Clinical experience with retrograde lung preservation.

Previous reports and our own experimental work suggest increased vascularity of the tracheobronchial wall when retrograde lung preservation is used. This principle was clinically applied in 21 consecutive lung transplant recipients (10 single and 11 bilateral). Lung preservation was achieved via the left atrial appendage and drainage was obtained through the pulmonary artery. Pneumoplegic preservation was achieved with modified Euro-Collins solution. Cardioplegia was induced by the standard method and the heart, harvested by different teams, did not exhibit left ventricular dilatation. Thirty-two bronchial anastomoses without wrapping were performed. No primary lung graft failure was documented. Cardiopulmonary bypass was instituted in three cases of pulmonary hypertension; however, this was deemed unnecessary in the remainder of the cases of bilateral transplantation while the second organ was being implanted. All bronchial anastomoses were followed between 2 and 28 months. A single instance of bronchial anastomosis dehiscence was observed on the 30th postoperative day. However, no stents were employed in this series, and no strictures or anastomotic granulomas have been reported so far. All the hearts could be used satisfactorily except for one primary graft failure. In conclusion, retrograde lung preservation is feasible in clinical lung transplantation, with simultaneous harvesting of the heart. The impact of retrograde lung preservation on the late clinical outcome remains to be seen.

Anastomosis, Surgical↗
PubMed1996

The meaning of psychological symptoms: effectiveness of a group intervention with hypochondriacal patients.

A group treatment for hypochondriasis was administered to 14 subjects. It was based on Barsky, Geringer and Wool (1988) [General Hospital Psychiatry, 10, 322-327] cognitive-behavioral formulation and presented as an educational course to explain the origins of an enhanced perception of somatic symptoms. Initially, one experimental group (N = 9) and a waiting list control (N = 8) were formed. Experimental subjects showed significant reductions in illness fears and attitudes, reported somatic symptoms and dysfunctional beliefs. Waiting-list controls also changed some illness attitudes, but showed no change in somatic symptoms and increased the number of visits to doctors. Experimental and control subjects differed on several change measures. Afterwards, part of the waiting list subjects (N = 5) received treatment. Overall, treatment was effective for the target measures and produced long-term positive effects on other fears, dysphoric mood and well-being. After treatment, subjects were significantly more extroverted, open and warm. The clinical impression was that treatment was not limited to less severe cases.

Adolescent↗
PubMed1996

[Infections in lung transplantation].

Lung transplantation has become the therapeutic hope of terminal respiratory patients. Infections are among the main causes of morbidity and mortality in these patients. We therefore analyze infections suffered after lung transplants performed at Clínica Puerta de Hierro over a two-year period. The cases of 14 transplanted patients, 6 bilateral and 8 unilateral, were analyzed. Pre-transplant data available for all included analysis of serum antibodies to several viruses, as well as bacterial and fungal cultures, and Ziehl's sputum test. All received prophylactic antibiotic, antifungal and antiviral treatment according to protocol. The bronchial aspirate of the donor, and recipient specimens of bronchial aspirate, bronchoalveolar lavage and biopsies obtained by bronchoscopy after transplantation were cultured. Bronchoscopies were performed according to protocol, based on clinical picture. Other cultures were obtained as needed. We recorded 27 respiratory infections, among which 4 were pneumonia transmitted by the donor, 3 were tuberculosis, 3 were Aspergillus infections, 5 were cytomegalovirus pneumonitis and one, P. carinii pneumonia. Lung infections have a strong impact on outcome of lung transplant patients. Knowledge of the chronological development of infections made appropriate prophylaxis and early detection possible, such that survival during the first two years after transplantation was approximately 70% in our hospital.

Adult↗
PubMed1996

Assessment of the energetic role of endogenous substrates in the tail artery of rat by means of enzyme inhibitors.

The rat tail artery during a 180 min incubation period in a medium containing glucose plus oxfenicine (an inhibitor of fatty acid oxidation) did not show changes in the contractile responses to adrenaline. In a substrate-free medium the extent of the contractions underwent a slight decrease during the last 60 min of incubation. When the substrate-free medium contained 2-deoxyglucose (an inhibitor of glycolysis and glycogenolysis) or oxfenicine, the decline of the contractile activity developed faster and attained a similar extent with each inhibitor. When the substrate-free medium contained 2-deoxyglucose together with oxfenicine or methylpalmoxirate (an inhibitor of fatty acid oxidation) the arteries displayed a pronounced and early fall in the contraction strength. These data suggest that in the presence of glucose the reserve substrates are not necessary as fuel source for the arterial contractions. However, in substrate-free conditions they constitute an important energy source. Furthermore, glycogen and triacylglycerol share the supply of energy and there does not seem to be any other reserve material in the smooth muscle of the rat tail artery.

Animals↗
PubMed1996

Exogenous substrates as energy source for the contractile activity of the isolated rat tail artery.

The isolated rat tail artery underwent a pronounced depression of the contractile responses to adrenaline during the incubation in a glucose-free medium containing 2-deoxyglucose and/or oxfenicine in order to inhibit the utilization of glycogen and/or endogenous triacylglycerol. When glucose was returned after 90 min of exposure to oxfenicine, the contraction strength recovered completely. In the medium with 2-deoxyglucose the addition of palmitate or hexanoate produced a recovery level 28% and 16% below the control values respectively. The effect of palmitate was nearly abolished and that of hexanoate partially decreased in the medium containing both inhibitors. Under this condition pyruvate reestablished the extent of the contraction to about 80% of the control value whereas beta-hydroxybutyrate produced a weak and transient recovery. These data suggest that in the tail artery the major portion of the energy needed to sustain the contractile activity is supplied by the oxidation of the more important plasmatic substrates with the exception of ketone bodies. However the Embden-Meyerhof pathway seems necessary to maintain at least a fraction of the contraction strength.

Animals↗
PubMed1995

Defective myosin VIIA gene responsible for Usher syndrome type 1B.

Usher syndrome represents the association of a hearing impairment with retinitis pigmentosa and is the most frequent cause of deaf-blindness in humans. It is inherited as an autosomal recessive trait which is clinically and genetically heterogeneous. Some patients show abnormal organization of microtubules in the axoneme of their photoreceptors cells (connecting cilium), nasal ciliar cells and sperm cells, as well as widespread degeneration of the organ of Corti. Usher syndrome type 1 (USH1) is characterized by a profound congenital sensorineural hearing loss, constant vestibular dysfunction and prepubertal onset of retinitis pigmentosa. Of three different genes responsible for USH1. USH1B maps to 11q13.5 (ref. 10) and accounts for about 75% of USH1 patients. The mouse deafness shaker-1 (sh1) mutation has been localized to the homologous murine region. Taking into account the cytoskeletal abnormalities in USH patients, the identification of a gene encoding an unconventional myosin as a candidate for shaker-1 (ref. 14) led us to consider the human homologue as a good candidate for the gene that is defective in USH1B. Here we present evidence that a gene encoding myosin VIIA is responsible for USH1B. Two different premature stop codons, a six-base-pair deletion and two different missense mutations were detected in five unrelated families. In one of these families, the mutations were identified in both alleles. These mutations, which are located at the amino-terminal end of the motor domain of the protein, are likely to result in the absence of a functional protein. Thus USH1B appears as a primary cytoskeletal protein defect. These results implicate the genes encoding other unconventional myosins and their interacting proteins as candidates for other genetic forms of Usher syndrome.

Adult↗
PubMed1995

A type VII myosin encoded by the mouse deafness gene shaker-1.

Genetic deafness is common, affecting about 1 in 2,000 births. Many of these show primary abnormalities of the sensory neuroepithelia of the inner ear, as do several hearing-impaired mouse mutants, suggesting that genes involved in sensory transduction could be affected. Here we report the identification of one such gene, the mouse shaker-1 (sh1) gene. Shaker-1 homozygotes show hyperactivity, head-tossing and circling due to vestibular dysfunction, together with typical neuroepithelial-type cochlear defects involving dysfunction and progressive degeneration of the organ of Corti. The sh1 gene encodes an unconventional myosin molecule of the type VII family. Three mutations are described, two mis-sense mutations and a splice acceptor site mutation, all in the region encoding the myosin head. The myosin type VII molecule encoded by sh1 is the first molecule to be identified that is known, by virtue of its mutations, to be involved in auditory transduction.

Amino Acid Sequence↗
PubMed1995

Order-disorder in T, T', and T* phase: superconductors and related materials.

After reviewing microstructural studies on superconducting materials showing T, T', and T* structural types, results are presented on the microstructure of some n-type superconductors and related materials prepared with accurate control of the oxygen stoichiometry. Electron microscopy is used to describe the ordering of interstitial oxygen defects in T-type La2NiO4 + delta leading to the formation of the n = 2 term of a homologous series with the general formula La8nNi4nO16n + 1. Structural transitions and superstructure formation in the Pr2-x-yCexSryCuO4-delta system are reported, where T, T', and T* phases are isolated as a function of both Ce and Sr content.

Electric Conductivity↗
PubMed1995

Surgical treatment of childhood mediastinal tuberculous lymphadenitis.

Between 1985 and 1991, we treated 6 children, aged 2 months to 3 years, who required an invasive procedure for the management of complications caused by enlarged mediastinal lymph nodes secondary to tuberculosis. Radiologic and endoscopic studies revealed bronchial involvement by lymph nodes, with endobronchial granulomas and lobar or pulmonary obstruction in 4 patients and marked tracheal and esophageal stenosis produced by extrinsic compression in the remaining 2. Pathologic study of the lymph node or bronchial samples from the 6 patients disclosed granulomas with caseous necrosis and Langhans' giant cells. All the children were treated with a standard 6-month drug regimen consisting of isoniazid, rifampicin, and pyrazinamide. Five of the patients underwent thoracotomy for the purpose of nodal curettage or excision. In 1, upper right lobectomy and bronchoplasty were necessary. The sixth patient was treated by endoscopic resection of the granulomas. There was no postoperative morbidity, and radiologic and endoscopic evidence of resolution of the lesions was observed in all the patients. In our experience, surgical treatment, when performed as a coadjuvant treatment for tracheobronchial complications stemming from mediastinal tuberculous lymphadenitis, results in the resolution of the lesions and has no related morbidity.

Bronchoscopy↗
PubMed1995

[The usefulness of 99mTc-tetrofosmin in the diagnosis of pulmonary tumors. A preliminary assessment].

We conducted a preliminary study of captation of the new radiopharmaceutical 99mTc-tetrofosmin in cases of primary carcinoma of the lung, analyzing the results of 5 cases studied before surgery with single photon emission tomography (SPECT) of the lung. The results obtained by imaging were compared with those from surgery. Tumor size ranged between 3.5 and 9 cm. In all cases the images showed that captation of the radiotracer by the neoplasm was satisfactory, leaving the area of the tumor clearly distinguishable from normal adjacent lung tissue and giving no signs of interference caused by absorption of 99mTc-tetrofosmin by contiguous structures (heart or liver). Based on these preliminary results we assert that SPECT of the lung using 99mTc-tetrofosmin may be useful in the clinical diagnosis of malignant lung tumors, although further research must determine to what extent the technique can be relied upon.

Adenocarcinoma↗
PubMed1995

Beneficial effects of oxfenicine on the hypoxic rat atria.

During hypoxia the isolated rat atria released lactate into the bathing medium and underwent a rise of resting tension and a decline of the peak developed tension and pacemaker frequency. The atria from 24 h fasted rats, which oxidize faster their endogenous triacylglycerol pool, showed greater functional disturbances during hypoxia and a smaller recovery after reoxygenation than those from fed rats. Oxfenicine, which is a selective inhibitor of carnitine palmitoyltransferase I, attenuated the rise of resting tension and improved the post-hypoxic recovery of peak tension in the atria from fasted rats. The decline of the pacemaker frequency as well as the lactate output were not altered by the inhibitor. Present data show that oxfenicine ameliorated some of the hypoxic functional disturbances. Inasmuch lactate output did not change and these effects manifested only in the atria predisposed to the utilization of endogenous lipids, it may be inferred that oxfenicine preserved the atrial functions through the inhibition of fatty acid oxidation.

Animals↗
PubMed1995

Effects of L-carnitine on the hypoxic atria from fed and fasted rats.

The aim of the investigation was to assess whether L-carnitine, an essential cofactor in the mitochondrial transfer of fatty acids, would ameliorate the hypoxic-induced disturbances in the isolated rat atria. During hypoxia, the atria released lactate into the bathing medium and underwent a rise in resting tension and a decline of the peak developed tension and pacemaker frequency. The atria from 24-h fasted rats, which oxidize faster their endogenous triacylglycerol stores>> exhibited greater functional disturbances during hypoxia and a smaller recovery after reoxygenation, with respect to the fed rats' atria. Furthermore, at the end of the hypoxic incubation the fasted rats atria displayed a reduction of the free CoA content together with a 3-fold increase in the content of long-chain fatty-acyl CoA, in comparison with those of fed rats. The addition of 5 mM L-carnitine 60 min before the onset of hypoxia did not exert any effect on the hypoxic atria. In contrast, 20 mM L-carnitine accelerated the decline of the pacemaker activity in the fasted rat atria and worsened the contracture development in both nutritional states. The fall of the peak tension and the posthypoxic recovery as well as the levels of free CoA and long-chain fatty-acyl CoA, and lactate output, were not affected by 20 mM L-carnitine treatment. These data suggest that L-carnitine is not beneficial for the hypoxic rat atria, even in the fasted state, wherein the atrial fatty acid catabolism is increased.

Animals↗
PubMed1994

Extended cervical mediastinoscopy: prospective study of fifty cases.

To assess the usefulness of extended cervical mediastinoscopy (ECM) in the staging of bronchogenic carcinoma, an ECM was performed prospectively in 50 patients with bronchogenic carcinoma of the left lung. The ECM was used after evaluation of disease operability and computed tomographic findings, and was performed simultaneously with standard cervical mediastinoscopy. In ECM, using the same cervical incision as in a standard cervical mediastinoscopy, dissection is performed behind the anterior face of the sternum. The aortic arch is reached at the level of the origin of the innominate artery. The mediastinoscope is then passed by sliding it along the left anterolateral face of the aortic arch until it reaches the aortopulmonary window. Extended cervical mediastinoscopy was considered positive when a nodal biopsy result consistent with a neoformative process or direct invasion of the mediastinal structures was found. Four patients with positive standard cervical mediastinoscopy and negative ECM were excluded. A false negative ECM was defined as the presence of infiltrated adenopathies at the paraaortic level detected on postoperative histologic study. The ECM was positive in 5 patients in whom operation was contraindicated. Resectability in the remaining 41 patients was 97.6%. Postoperative pathologic study showed infiltrated adenopathy in 3 patients (2 subcarinal, 1 subaortic) accounting for 40 true negatives (the subcarinal group is inaccessible by ECM). This study suggests that ECM has outstanding specificity (100%), sensitivity of 83.3%, and a diagnostic accuracy of 97.8%. A positive predictive value of 100% and a negative predictive value of 97.5% were also identified by this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗