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Biomedical subjects

A Varela

Publications and source records attributed to A Varela.

At least 19 recordsLinked to original sources
PubMed2003

Effect of acute nitric oxide synthase inhibition in the modulation of heart rate in rats.

Acute nitric oxide synthase inhibition with N G-nitro-L-arginine methyl ester (L-NAME) on chronotropic and pressor responses was studied in anesthetized intact rats and rats submitted to partial and complete autonomic blockade. Blood pressure and heart rate were monitored intra-arterially. Intravenous L-NAME injection (7.5 mg/kg) elicited the same hypertensive response in intact rats and in rats with partial (ganglionic and parasympathetic blockade) and complete autonomic blockade (38 +/- 3, 55 +/- 6, 54 +/- 5, 45 +/- 5 mmHg, respectively; N = 9, P = NS). L-NAME-induced bradycardia at the time when blood pressure reached the peak plateau was similar in intact rats and in rats with partial autonomic blockade (43 +/- 8, 38 +/- 5, 46 +/- 6 bpm, respectively; N = 9, P = NS). Rats with combined autonomic blockade showed a tachycardic response to L-NAME (10 3 bpm, P<0.05 vs intact animals, N = 9). Increasing doses of L-NAME (5.0, 7.5 and 10 mg/kg, N = 9) caused a similar increase in blood pressure (45 +/- 5, 38 +/- 3, 44 +/- 9 mmHg, respectively; P = NS) and heart rate (31 +/- 4, 34 +/- 3, 35 +/- 4 bpm, respectively; P = NS). Addition of L-NAME (500 micro M) to isolated atria from rats killed by cervical dislocation and rats previously subjected to complete autonomic blockade did not affect spontaneous beating or contractile strength (N = 9). In vivo results showed that L-NAME promoted a tachycardic response in rats with complete autonomic blockade, whereas the in vitro experiments showed no effect on intrinsic heart rate, suggesting that humoral mechanisms may be involved in the L-NAME-induced cardiac response.

Analysis of Variance↗
PubMed2003

[Prognostic factors of early morbidity and mortality after lung transplantation].

OBJECTIVES: Despite years of experience with lung transplantation, the rate of perioperative mortality remains high. The objective of this study was to look at our experience in the early postoperative period following lung transplantation in an effort to identify possible pre-, intra- and postoperative risk factors associated with mortality. PATIENTS AND METHODS: A retrospective study of 68 consecutive patients receiving lung transplants over a period of 56 months. The conditions that led to transplantation were obstructive disease (40%), interstitial disease (33%) and suppurative disease (27%). Pre-, intra- and postoperative characteristics of donors and recipients were analyzed for their relation to morbidity and mortality. Statistical studies were done using SPSS 10.0 software. A p-value less than.05 was considered significant. Univariate analysis identified variables associated with the incidence of mortality in the postoperative recovery unit, and the variables with statistically significant associations were entered into multivariate analysis, using a logistic regression model to calculate odds ratio (OR) and 95% confidence intervals (CI). RESULTS: No donor variables correlated with mortality. Patients with suppurative lung disease had a lower mortality rate (0% vs 30%; P = 0.04). Mortality was related to ischemic time longer than 300 minutes (OR = 2) and the use of extracorporeal circulation (OR = 4). A PaO2/FiO2 ratio less than 150 during the first 24 hours following transplantation (OR = 5) and reoperation due to bleeding (OR = 12) were the variables showing the highest correlations with mortality during the early postoperative period. CONCLUSIONS: The mortality rate during the early postoperative period in our series was 22%. The survival rate was better in patients with suppurative lung disease. Bleeding that required reoperation and early graft dysfunction (defined in part by a PaO2/FiO2 ratio less than 150 during the first 24 hours) were the variables that best predicted death in the early postoperative period following lung transplantation.

Adolescent↗
PubMed2002

Effects of fasting and hypoxic preconditioning on the hypoxic-reoxygenated ventricular strips of the rat heart.

The investigation aimed to assess the effects of hypoxic preconditioning in right ventricle strips of fed and 24-h fasted rats, which display a fast fatty acid catabolism, and to ascertain whether these effects are associated with changes in the tissue levels of long-chain acylCoA and acyl carnitine and glycolytic activity. Strips were mounted isometrically in Krebs-bicarbonate solution with 10 mM dextrose and paced at 1 Hz. Strips were exposed to 30 min hypoxia and 60 min reoxygenation with or without a previous preconditioning cycle of 5 min hypoxia followed by a 10 min reoxygenation. During hypoxia the fasted rat strips underwent a greater contracture with respect to the fed group. Preconditioning reduced the contracture strength and accelerated the post-hypoxic recovery only in the fasted rat strips. Hypoxia evoked an increase in the acylCoA and acyl carnitine tissue-contents of the strips which reached higher levels in the fasted than in the fed rat groups. Preconditioning had no effects on the content of these metabolites. During hypoxia lactate output was lower in the fasted than in the fed rat strips and preconditioning abolished this decrease. These data suggest that the protective effects of hypoxic preconditioning occur in the heart tissue predisposed to the oxidation of fatty acid and can not be ascribed to changes in the accumulation of acylCoA and acyl carnitine but could be due, at least in part, to an activation of glycolysis.

Acyl Coenzyme A↗
PubMed2002

Influence of fasting on the effects of ischemic preconditioning in the ischemic-reperfused rat heart.

The effects of fasting and ischemic preconditioning (IP) on heart function of Langendorff-perfused rat hearts exposed to 25 min global ischemia plus 30 min reperfusion (RP), were correlated with lactate release and tissue-levels of long-chain acyl carnitine (LCCa) and CoA (LCCoA). IP was achieved by a 3 min ischemia plus a 5 min reperfusion cycle. Creatine kinase leakage was measured to assess the extent of cardiac injury. Fasting reduced the ischemic-induced contracture, improved RP recovery of mechanical function, reduced lactate release and increased the end-ischemia LCCoA and LCCa levels. Both in the fed and the fasted rat hearts IP delayed the pacemaker depression, reduced the amplitude of ischemic contracture and improved the RP recovery of contraction. However, IP reduced creatine kinase and lactate release only in the fed rat hearts. IP had no effects on tissue LCCa and LCCoA in both groups. These data suggest that: 1) beneficial effects of fasting may be ascribed, at least in part, to a reduced lactate production which may attenuate ischemic myocyte acidification and to the accumulation of fatty acyl esters which would favour citric acid cycle replenishment during RP. 2) beneficial effects of IP could be in part explained by the reduction of lactate production in the fed group although data obtained with the fasted rat heart indicate that another mechanisms must also be involved in the effects of IP. 3) accumulation of LCCoA and LCCa is not involved in the noxious effects of ischemia as well as in the protection effected by IP.

Animals↗
PubMed2002

[Study of pulmonary lesions with (99m)Tc-Tetrafosmin and chest spect. Determination of uptake related factors, diagnostic value and prognosis].

One hundred fifteen patients with 119 pulmonary lesions in which malignancy was suspected underwent a SPECT study with 99mTc-Tetrofosmin (TTF) to assess the possible factors involved in the uptake of the radiopharmaceutical. The TTF uptake rate in the lung tumor with respect to that of healthy tissue (TTF index) was evaluated in terms of: benignity and malignancy, histological type, stage, cell differentiation, size, necrosis, survival and the influence of P-glycoprotein (Pgp), detected by immunohistochemistry, on the TTF uptake. The mean TTF index in the 18 benign lesions studied was 1.01 0.05, while that of the 101 malignant lesions was 1.59 0.45 (p < 0.001), with a positive predictive value of 97.7% and a negative predictive value of 50%. The comparison of the histological types, degree of cell differentiation, necrosis and stage revealed no statistically significant differences. With respect to size, those tumors measuring > 3 cm showed greater uptake than smaller lesions. In patients with non-small cell lung cancer, a positive relationship was observed between the TTF index and survival, a circumstance that did not occur in patients with small cell lung cancer. In the cases in which the presence of Pgp was assessed, there was an inverse relationship between the TTF ratio and Pgp expression. In conclusion, thoracic SPECT with 99mTc-TTF has a high positive predictive value for the presence of lung cancer, although a negative study does not rule out the existence of the disease. The reason for this is the inverse relationship between 99mTc-TTF uptake and the density of Pgp expression.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Transition from the layered Sr2RhO4 to the monodimensional Sr4RhO6 phase.

Study of the structural changes occurring during the reduction process of the Sr2RhO4+delta, (214), n=1 term of the Ruddlesden and Popper series, shows that for delta <0.02 values, this material dissociates into the Sr4RhO6 (416) monodimensional phase, alpha = infinity, beta = 0 compound of the (A3B2O6)alpha-(A3B3O9)beta family, and Rh metal. During the first stage, this process occurs by the formation of an intergrowth between the (214) and (416) materials which can be only detected by high resolution electron microscopy and is easily interpreted on the basis of the structural relationship established between them. Further reduction allows the segregation of both phases as separated entities, which coexist with Rh metal. The dissociation process is reversible and, under oxidizing conditions, a layered material with anionic composition delta =0.06 is always obtained. This behaviour seems to be a general way of accommodating the compositional changes in layered A2BO4 phases where the B cation is always in a octahedral environment. The structural mechanism of this transformation is proposed, and the structural relationship between these two low-dimensional oxides is established.

Journal Article↗
PubMed2001

Strengthening user participation through health sector reform in Colombia: a study of institutional change and social representation.

The challenge of achieving community participation as a component of health sector reform is especially great in low- and middle-income countries where there is limited experience of community participation in social policy making. This paper concentrates on the social representations of different actors at different levels of the health care system in Colombia that may hinder or enable effective implementation of the participatory policy. The study took place in Cali, Colombia and focused on two institutional mechanisms created by the state to channel citizen participation into the health sector, i.e. user associations and customer service offices. This is a case study with multiple sources of evidence using a combination of quantitative and qualitative social science methods. The analysis of respondents' representations revealed a range of practical concerns and considerable degree of scepticism among public and private sector institutions, consumer groups and individual citizens about user participation. Although participation in Colombia has been introduced on political, managerial and ethical grounds, this study has found that health care users do not yet have a meaningful seat around the table of decision-making bodies.

Attitude to Health↗
PubMed2001

Antisense inhibition of brain renin-angiotensin system decreased blood pressure in chronic 2-kidney, 1 clip hypertensive rats.

The systemic renin-angiotensin system (RAS) plays an important role in blood pressure (BP) regulation during the development of 2-kidney, 1 clip (2K1C) hypertension. Its contributions decrease with time after constriction of the renal artery. During the chronic phase, the peripheral RAS returns to normal, but the hypertension is sustained for months. We hypothesized that in this phase the brain RAS contributes to the maintenance of high BP. To test the hypothesis, we studied the role of brain RAS by decreasing the synthesis of angiotensinogen (AGT) and the angiotensin II (Ang II) type 1a receptor (AT(1)R) with intracerebroventricular injections of antisense oligonucleotides (AS-ODNs). The response of systolic BP (SBP) to AS-ODNs to AGT mRNA was studied in 2K1C rats at 6 months after clipping, and the response to AS-ODNs to AT(1)R mRNA was studied at 10 months after clipping. Intracerebroventricular injection of AS-ODN-AGT (200 microgram/kg, n=5) significantly decreased SBP (-22+/-6 mm Hg, P<0.05) compared with the sense ODN (n=5) and saline (n=3) groups. Intracerebroventricular injection of AS-ODN-AGT reduced the elevated hypothalamic Ang II level. The hypothalamic Ang II content in sense ODN and saline groups was significantly (P<0.05) higher than in the nonclipped group. Compared with inverted ODN, intracerebroventricular injection of AS-ODN-AT(1)R (250 microgram/kg, n=6) significantly decreased SBP (-26+/-8 mm Hg, P<0.05) for 3 days after injection. This was a brain effect because intravenous AS-ODN-AT(1)R at a dose of 250 to 500 microgram/kg did not affect SBP. These results suggest that the brain RAS plays an important role in maintaining the elevated SBP in chronic 2K1C hypertension.

Angiotensin II↗
PubMed2001

Presence of encysted immature nematodes in a released whooping crane (Grus americana).

Numerous nematode cysts were observed throughout the mesentery and on the surface of gastrointestinal organs in a whooping crane (Grus americana) that was found dead in a central Florida marsh. Morphology of the excysted nematodes most closely resembled third-stage larvae in the order Spirurida but were not similar to any species previously reported in whooping cranes. Evidence presented suggests that the larvae may be Physocephalus sexalatus, a swine spirurid in the subfamily Ascaropsinae that is commonly found encapsulated in birds, amphibians, and reptiles. We suspect that the whooping crane may potentially serve as a transport host for this parasite.

Animals↗
PubMed2000

Association of HLA-DRB1*1602 and DRB1*1001 with Takayasu arteritis in Colombian mestizos as markers of Amerindian ancestry.

We performed HLA Class I and Class II typing in 16 patients (15 women, one man) with a confirmed diagnosis of Takayasu arteritis. We did not find any of the previously described associations with HLA-B52, and/or HLA-DRB1*1301 alleles. However, in our patients, HLA-DRB1*1602 and HLA-DRB1*1001 were significantly increased. The association of Takayasu arteritis with Amerindian and Asian HLA-DRB1 alleles (DRB1*1602 and DRB1*1001) in the Colombian mestizo patients reported here, and with HLA-B*3906 previously reported in Mexicans, suggest the possibility that some HLA and disease associations are markers for ethnicity of a population carrying a disease gene which is present in an admixed population with the disease.

Adolescent↗
PubMed2000

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

Hypoxic preconditioning (PC) was studied using rat atria set up isometrically in 10 mM dextrose medium and paced at 1 Hz, applying three different protocols wherein fed and 24-h fasted rats were used in protocols 1 and 2 and only the fed in protocol 3. In protocol 1, PC was achieved applying a 5 min hypoxia followed by 10 min of reoxygenation before the onset of a 60 min hypoxia and 60 min reoxygenation. In protocol 2 the 5 min and a posterior 45 min hypoxia were applied in the absence of dextrose whereas in the 10 min and 60 min reoxygenation periods dextrose was present. In protocol 3, two cycles of 5 min dextrose-free hypoxic periods were applied before the sustained hypoxia (dextrose-free) and reoxygenation periods (10 min and final 45 min, both in the presence of dextrose). In the control groups of all protocols, the equilibration periods were prolonged to compensate the duration of PC. In the control groups of protocols 1 and 2, the sustained hypoxia evoked greater disturbances of contractility and a smaller post-hypoxic recovery in the fasted than in the fed rat atria. In protocol 1, PC markedly reduced the rise in resting tension and improved the post-hypoxic recovery in the fasted rat atria whereas in the fed rat atria protective effects were small and brief. In protocol 2, PC evoked a small reduction of contracture only in the atria from fasted rats and in protocol 3, PC exacerbated the hypoxic disturbances. These data suggest that PC effects depend both on the severity of the PC stress and the sustained hypoxia; and that PC does not require coronary flow.

Animals↗