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Biomedical subjects

L F Moreira

Publications and source records attributed to L F Moreira.

At least 19 recordsLinked to original sources
PubMed2001

Partial left ventriculectomy in severe idiopathic dilated cardiomyopathy: assessment of short-term results and their impact on late survival by magnetic resonance imaging.

We evaluated short-term effects of partial ventriculectomy on left ventricular (LV) parameters and its impact on late survival by magnetic resonance imaging (MRI). Twenty patients and 10 normal volunteers were studied, and LV volumes (EDV, ESV), ejection fraction (EF), short- and long-axis dimensions (SA, LA), wall thickness (Wth), shape (LA/SA), geometry (Wth/SA), a geometry index (Phi), and wall-motion score index (WMSI) were evaluated pre- and postoperatively. Also, we compared results and survival of patients with preoperative EF 17%. Short-term results showed significant changes (P < 0.001) in: EF (17.3 +/- 7.3% vs. 30.4 +/- 9.5%), EDV (391.9 +/- 118 vs. 272.7 +/- 90 mL); ESV (308.2 +/- 102.8 vs. 190.3 +/- 68.4 mL); SA (80.5 +/- 10.4 vs. 71.7 +/- 7.8 mm); LA/SA (1.13 +/- 0.1 vs. 1.34 +/- 0.1); Wth (8.35 +/- 0.99 vs. 9.75 +/- 1.41 mm); Wth/SA (0.10 +/- 0.01 vs. 0.14 +/- 0.02), diastolic( 0.80 +/- 0.16 vs. 0.58 +/- 0.13) and systolic (0.78 +/- 0.18 vs. 0.55 +/- 0.12) Phi; and WMSI (-2 vs. -1) (P = 0.032). The EF division showed differences in: LA/SA (1.26 +/- 0.10 vs. 1.49 +/- 0.12) (P < 0.001); Wth/SA (0.13 +/- 0.02 vs. 0.15 +/- 0.02) (P = 0.023); diastolic (0.65 +/- 0.11 vs. 0.48 +/- 0.11) and systolic (0.63 +/- 0.09 vs. 0.46 +/- 0.09) Phi (P < 0.001); and WMSI (-2 vs. -1) (P = 0.033). Finally, correlation between pre/postoperative EF showed for EF < 17%, r = 0.32 and for EF >17%, r = 0.83, which had different late survival. Our study showed significant changes on LV parameters after ventriculectomy. Patients with EF >17% showed better EF correlation between pre/postoperative values and higher survival rate. J. Magn. Reson. Imaging 2001;13:781-786.

Adult↗
PubMed2001

Histopathological findings in skeletal muscle used in human dynamic cardiomyoplasty.

Patients submitted to dynamic cardiomyoplasty had an initial clinical improvement followed by a decrease in cardiac failure indices. A histopathological study of the skeletal muscle was undertaken to explain this. Latissimus dorsi fragments from 15 patients submitted to dynamic cardiomyoplasty in a 1:1 (heart beat:muscle stimulation) conditioning were analysed by light microscopy. The interval between surgery and obtaining the specimens (13 from necropsies, two from heart transplants) ranged from 37 days to 6 years. Nuclear clumps and internalization, the presence of round fibres, inflammation, and fibrosis were analysed semi-quantitatively; the thickness of muscle fibres and the percentage of tissue fat were measured by image analysis. The quantitative data were also compared, in 12 cases, with gender- and age-matched necropsy controls. The mean thickness of muscle fibres in cases and controls was 27.21+/-5.33 and 40.84+/-9.42 microm, respectively (p=0.001). The percentage of tissue fat in cases and controls was 12.04+/-12.66% and 0.93+/-0.91%, respectively (p=0.008). The duration of grafts correlated positively with the quantity of nuclear clumps (R=0.80, p<0.001) and round fibres (R=0.53, p=0.04), as well as with the percentage of tissue fat (R=0.68, p=0.005). Accordingly, a negative correlation was found between the duration of grafts and the mean diameter of fibres, characterizing muscle atrophy (R=-0.66, p=0.01). The longer the post-surgical period, the more intense the degenerative lesions. This study shows that skeletal muscle used in human dynamic cardiomyoplasty may atrophy and be replaced by fat when stimulation is synchronized to every cardiac beat. These findings could play a role in explaining the long-term results of this surgical procedure.

Adipose Tissue↗
PubMed2001

Current perspectives of partial left ventriculectomy in the treatment of dilated cardiomyopathy.

OBJECTIVES: Partial left ventriculectomy has been performed as an alternative to heart transplantation in the treatment of severe cardiomyopathies. This investigation documents the clinical and left ventricular (LV) function effects of this procedure, associated, when necessary, with mitral insufficiency correction, in 43 patients with idiopathic dilated cardiomyopathy. METHODS: Eighteen patients were in New York Heart Association class III and 25 in class IV. Seven of them were operated in cardiogenic shock. The procedure was associated with mitral annuloplasty in 32 patients and mitral replacement in three. RESULTS: Nine patients (20.9%) died during the hospital period and the cause of death was associated with ventricular failure in seven patients. The other patients were followed up from 2 to 57 months (mean, 28.3 months). At 6 months of follow-up, eight patients were in functional class I, 13 in class II, three in class III and one patient was in class IV (P<0.001). On the other hand, nine patients died during the first 6 months and another six in the later postoperative period. The cause of late death was progressive heart failure in eight patients, and seven patients died because of arrhythmia related events. The actuarial survival was 58.1+/-7.5% at 1 year and 43.9+/-8.1% at 4 years of follow-up. Regarding ventricular function modifications, the LV diastolic volume decreased by around 25% and the LV ejection fraction increased from 17.8+/-4.7 to 22.3+/-7.9% (P<0.001), whereas significant changes in the cardiac index, stroke index and pulmonary pressures were also found 1 month after the operation. In the later follow-up, despite the maintenance of hemodynamic improvement, the LV diastolic volume tended to increase and returned to preoperative levels at 4 years, while a concomitant decrease in the LV ejection fraction was also observed. CONCLUSION: Partial left ventriculectomy associated with mitral insufficiency correction improves LV function and ameliorates congestive heart failure in patients with idiopathic cardiomyopathy. Otherwise, the LV function benefits seem to be restricted by the possibility of progressive LV redilatation. Furthermore, the clinical application of this procedure is limited by the high mortality observed in the first postoperative months and by the possibility of heart failure progression and arrhythmia related events at late follow-up.

Adult↗
PubMed2001

Dynamic cardiomyoplasty as a therapeutic alternative: current status.

Dynamic cardiomyoplasty was proposed as an alternative surgical treatment for severe cardiomyopathies and has been performed worldwide in more than 1,000 patients. Patients indicated for this procedure are specifically those with dilated or ischemic cardiomyopathies. The ventricular function improvement observed after dynamic cardiomyoplasty derived from the direct action of synchronized skeletal muscle flap contraction and from a girdling effect that helps to reverse chamber remodeling and to decrease ventricular wall stress. Although long-term benefits of this procedure may be limited by skeletal muscle flap ischemic compromise, technological advances incorporated in the new myostimulators will possibly decrease this complication incidence. Clinical improvement has been reported as a consistent finding in cardiomyoplasty follow-up and the overall 5-year survival after this procedure ranges from 39 % to 54 %. On the other hand, the mortality after cardiomyoplasty has been significantly higher for patients in persistent New York Heart Association functional class IV, showing that this procedure needs to be indicated earlier than the heart transplantation. In this regard, only the results of an ongoing randomized trial will potentially define cardiomyoplasty influence on the survival of patients with severe heart failure. In the meantime, however, there are clearly several functional class III patients whose quality of life and exercise capacity have worsened despite the use of maximum medical therapy, justifying dynamic cardiomyoplasty indication.

Cardiomyopathies↗
PubMed2001

Noninvasive diagnosis of allograft vascular disease after heart transplantation.

OBJECTIVE: To determine the predictive values of noninvasive tests for the detection of allograft vascular disease. METHODS: We studied 39 patients with mean ages of 48+/-13 years and a follow-up period of 86+/-13 months. The diagnosis of allograft vascular disease was made by cine-coronary arteriography, and it was considered as positive if lesions existed that caused > or =50% obstruction of the lumen. Patients underwent 24h Holter monitoring, thallium scintigraphy, a treadmill stress test, and dobutamine stress echocardiography. Sensitivity, specificity, and positive and negative predictive values were determined in percentages for each method, as compared with the cine-coronary arteriography results. RESULTS: Allograft vascular disease was found in 15 (38%) patients. The Holter test showed 15.4% sensitivity, 95.5% specificity. For the treadmill stress test, sensitivity was 10%, specificity was 100%. When thallium scintigraphy was used, sensitivity was 40%, specificity 95.8%. On echocardiography with dobutamine, we found a 63.6% sensitivity, 91.3% specificity. When the dobutamine echocardiogram was associated with scintigraphy, sensitivity was 71.4%, specificity was 87%. CONCLUSION: In this group of patients, the combination of two noninvasive methods (dobutamine echocardiography and thallium scintigraphy) may be a good alternative for the detection of allograft vascular disease in asymptomatic patients with normal ventricular function.

Adult↗
PubMed2000

Influence of biopump with and without intraaortic balloon on the coronary and carotid flow.

BACKGROUND: The objective of this study was to evaluate the influence of biopump used for left ventricular assistance on the coronary and carotid flows in dogs with normal heart. The efficacy of the simultaneous use of an intraaortic balloon pump to compensate the possible deleterious effects of the circulatory assistance with continuous flow was also analyzed. METHODS: Fifteen dogs were studied. The hemodynamic evaluation included serial measurements of the classic parameters. Carotid and coronary blood flows were obtained by electromagnetic transducers. RESULTS: The hemodynamic evaluation did not show significant statistical changes. The use of circulatory-isolated assistance with biopump shows reduction (24.6% +/- 6.1%) in coronary flow, in relation to the control situation and the concomitant use of biopump and intraaortic balloon pump showed similar coronary flow. Regarding carotid flow, a similar trend was observed in relation to the positive influence of the pulsatile flow with an intraaortic balloon pump without statistical significance (p = 0.0582). CONCLUSIONS: The biopump reduces the coronary flow in dogs. The use of intraaortic balloon pump with the biopump increases the coronary flow significantly, reaching similar values to those observed without the circulatory assistance.

Animals↗
PubMed2000

Autopsy findings in early and late postoperative death after partial left ventriculectomy.

BACKGROUND: Partial left ventriculectomy (PLV) is an alternative to heart transplantation for patients with severe heart failure. However, this procedure is accompanied by high morbidity and mortality. Therefore, we studied the hearts of 12 patients who underwent this procedure to increase our understanding of the causes of bad outcome. METHODS: We analyzed the autopsy hearts of 11 of 16 patients who died after PLV, and one heart from a patient who underwent heart transplantation. RESULTS: Six patients died less than 30 days postoperatively, 4 of cardiogenic shock, 1 of arrhythmia, and 1 of coagulopathy. Five patients died from 36 to 120 days after the procedure, 4 of cardiogenic shock and 1 of arrhythmia. The patient who underwent heart transplantation had a cardiogenic shock 230 days after PLV. Ten hearts weighed more than 500 g and nine had myocardial infarction that extended to the papillary muscles. Four patients had infarction of both papillary muscles and 3 of them had episodes of arrhythmia, suggesting some relation between these events. CONCLUSIONS: We found several important morphologic clues for bad outcome: infarction of both papillary muscles, which may be associated with the development of arrhythmia, and myocardial infarction and pericardial hemorrhage, which may contribute to the outcome of heart failure.

Adult↗
PubMed2000

Left ventricular regional wall motion, ejection fraction, and geometry after partial left ventriculectomy. Influence of associated mitral valve repair.

OBJECTIVE: Left partial ventriculectomy has been proposed for treatment of heart failure. We investigated the effects of isolated left partial ventriculectomy and left partial ventriculectomy associated with mitral annuloplasty on refractory heart failure due to idiopathic dilated cardiomyopathy. METHODS: Nineteen patients underwent partial left partial ventriculectomy associated with mitral annuloplasty and six patients isolated left partial ventriculectomy. In two patients the left partial ventriculectomy associated with mitral annuloplasty was combined with tricuspid annuloplasty. We evaluated before and after the surgery (24+/-14 days): the functional class, left ventricular ejection fraction (LVEF), right ventricular ejection fraction (EF), regional wall motion, hemodynamics, mitral regurgitation, left ventricular geometry and coronary angiography. RESULTS: For the overall group LVEF improved from 14.5+/-8.0 to 30.3+/-12.2% (P<0.0002) and right ventricular EF from 21.2+/-7.1 to 28.4+/-8.3% (P<0.002). In patients who underwent left partial ventriculectomy associated with mitral annuloplasty LVEF increased from 14.5+/-8.6 to 29.5+/-12.2% (P<0. 002). Isolated left partial ventriculectomy increased LVEF from 13. 5+/-7.5 to 31.5+/-11.1% (P<0.04). Distal segments of marginal branches of the circumflex artery were not visualized by coronary angiography. Left partial ventriculectomy associated with mitral annuloplasty reduced the wedge pressure from 25.0+/-12.1 to 18.0+/-7. 0 mmHg (P<0.03) and increased cardiac output from 3.8+/-0.8 to 4. 6+/-1.1 l/min (P<0.004), while isolated left partial ventriculectomy increased cardiac output from 3.7+/-1.0 to 4.8+/-1.3 l/min (P<0.03). Regional wall motion increment was more evident in anterolateral region from 4.2+/-6.8 to 14+/-8.3% (P<0.002) except in two patients. Left ventricular geometry changed in most patients, but a homogeneous pattern was not identified. Seven patients died during a mean follow-up of 546+/-276 days. Survivors had improvement in functional class. Augmentation of LVEF >5% was associated with a favorable clinical outcome with improvement in clinical status without death. CONCLUSIONS: Effects of left partial ventriculectomy are not necessarily dependent upon reduction of mitral regurgitation or changes in left ventricular geometry. However, risk of death after the surgery must be reduced for a clinical application.

Adult↗
PubMed2000

Permanent and temporary pacemaker implantation after orthotopic heart transplantation.

PURPOSE: To determine the indication for and incidence and evolution of temporary and permanent pacemaker implantation in cardiac transplant recipients. METHODS: A retrospective review of 114 patients who underwent orthotopic heart transplantation InCor (Heart Institute USP BR) between March 1985 and May 1993. We studied the incidence of and indication for temporary pacing, the relationship between pacing and rejection, the need for permanent pacing and the clinical follow-up. RESULTS: Fourteen of 114 (12%) heart transplant recipients required temporary pacing and 4 of 114 (3.5%) patients required permanent pacing. The indication for temporary pacing was sinus node dysfunction in 11 patients (78.5%) and atrioventricular (AV) block in 3 patients (21.4%). The indication for permanent pacemaker implantation was sinus node dysfunction in 3 patients (75%) and atrioventricular (AV) block in 1 patient (25%). We observed rejection in 3 patients (21.4%) who required temporary pacing and in 2 patients (50%) who required permanent pacing. The previous use of amiodarone was observed in 10 patients (71.4%) with temporary pacing. Seven of the 14 patients (50%) died during follow-up. CONCLUSION: Sinus node dysfunction was the principal indication for temporary and permanent pacemaker implantation in cardiac transplant recipients. The need for pacing was related to worse prognosis after cardiac transplantation.

Adolescent↗
PubMed1999

Lymphovascular and neural invasion in low-lying rectal carcinoma.

We have previously demonstrated that lymphovascular infiltration was correlated with an increased risk for developing lymph node metastasis in rectal adenocarcinomas confined within the submucosal layer. In another study, lymphovascular infiltration was also correlated with poor prognosis for patients with advanced rectal cancers. Considerations that low rectal tumors have an increased risk to develop recurrence and neural invasion have been recently implicated with a more localized pattern of tumor spread. We therefore assessed the lymphovascular and neural invasion in 65 specimens from patients with low rectal cancers who underwent curative operation to determine its implications in the treatment and prognosis. Lymphovascular invasion was noted in 60%, and neural invasion was found in 27% of the cases. Five-year survival rates (Kaplan-Meier method) were significantly decreased in patients with lymphovascular invasion (31 vs. 67%; p < 0.01) or neural invasion (30 vs. 58%; p < 0.01). Neither lymphovascular nor neural invasion was noted in Dukes' stage A tumors. There was no recurrence or distant metastasis in these patients. However, lymphovascular and neural invasion increased with tumor stage. Local recurrence and distant metastasis occurred respectively in three and four, and five and five patients with Dukes' B and C tumors, respectively. Both Dukes' B and C cases with local recurrence had a higher incidence of neural invasion as compared with the disease-free group. These results suggest that postoperative assessment of venous and neural invasion may provide valuable information to better determine which patients with low rectal cancers would benefit from adjuvant treatment.

Adenocarcinoma↗
PubMed1999

Paraplegia following intraaortic balloon circulatory assistance.

Intraaortic balloon counterpulsation is frequently used in patients experiencing severe ventricular dysfunction following maximal drug therapy. However, even with the improvement of percutaneous insertion techniques, the procedure has always been followed by vascular; infectious, and neurological complications. This article describes a case of paraplegia due to intraaortic balloon counterpulsation in the postoperative period of cardiac surgery.

Humans↗
PubMed1999

Total inversion of the left lung circulation: morphologic and functional analyses.

BACKGROUND: An experimental model for total inversion of left lung circulation was developed. With this model, the authors demonstrate that it is possible to reverse the pulmonary circulation and preserve the normal function and morphology of the lung. METHODS: Eight dogs had their left pulmonary circulation reversed. The blood from the pulmonary artery trunk was diverted to the pulmonary veins, and returned from the pulmonary artery into the left atrium. In order to monitor the flow through the reversed system, color Doppler echocardiography was performed on the ninth postoperative day. The dogs were reoperated after 15 days for re-evaluation. Blood gas analyses from the aorta and the pulmonary artery were used to study the functional status of the lung in both operations. The morphology was studied by comparing biopsies of the lung performed before and after reversal of flow. RESULTS: Blood gas analysis showed no significant difference between the samples of from the aorta and pulmonary artery. Color Doppler echocardiography was a reliable method for the study of the inverted circulation. The histological study showed no differences in the morphology of the lung after the reversed circulation. CONCLUSIONS: Left pulmonary circulation was fully reversed. Pulmonary function and morphology remained normal.

Animals↗
PubMed1998

Determinants of midterm outcome of partial left ventriculectomy in dilated cardiomyopathy.

BACKGROUND: Partial left ventriculectomy has been proposed for treatment of severe cardiomyopathies. This study reports midterm results of this procedure in 37 patients with dilated cardiomyopathy. METHODS: All patients were in New York Heart Association class III (16) or IV (21). Partial ventriculectomy was associated with mitral annuloplasty in 27 patients and with mitral replacement in 2. RESULTS: There were seven operative deaths (18.9%). During a mean follow-up of 18.2+/-9.3 months, 9 more patients died. Actuarial survival was 56.7%+/-8.1% at 6 and 24 months. Analysis of factors influencing outcome showed that midterm survival was significantly affected only by myocardial cell diameter. Otherwise, functional class improved from 3.5+/-0.5 to 1.8+/-0.9 in the survivors (p < 0.001). Furthermore, left ventricular diastolic volume decreased from 523+/-207 to 380+/-148 mL (p < 0.001), and left ventricular ejection fraction increased from 17.1%+/-4.6% to 23%+/-8% (p < 0.001), whereas significant changes in cardiac index, stroke index, and pulmonary pressures were found at 1 month of follow-up. Although left ventricular diastolic volume tended to increase in the late postoperative period, left ventricular ejection fraction and hemodynamic variables did not change significantly. CONCLUSIONS: Partial ventriculectomy improves left ventricular function and congestive heart failure in patients with dilated cardiomyopathy for up to 24 months of follow-up. Nevertheless, this procedure's clinical application is limited by the high mortality observed in the first postoperative months. Otherwise, new perspectives may be advised by the identification that partial ventriculectomy results seem to be influenced by compromised myocardial cells.

Adult↗
PubMed1998

Partial left ventriculectomy with mitral valve preservation in the treatment of patients with dilated cardiomyopathy.

OBJECTIVE: This study reports initial results of partial left ventriculectomy performed with preservation of the mitral valve in the treatment of 27 patients with idiopathic dilated cardiomyopathy. METHODS: Patients were in New York Heart Association class III or IV. Partial ventriculectomy was performed as an isolated procedure in four patients and associated with mitral annuloplasty in 23 patients. There were four hospital deaths (14.8%) and the remaining patients were followed for 11.2 +/- 6 months. RESULTS: Decrease of left ventricular diastolic diameter (81.8 +/- 8.7 to 68.5 +/- 7.6 mm, p < 0.001) and improvement of left ventricular wall shortening (12% +/- 3.1% to 18.1% +/- 3.9%, p < 0.001) were demonstrated by echocardiography after the operation. Left ventricular radioisotopic angiography showed reduction of diastolic volume (495 +/- 124 ml to 352 +/- 108 ml, p < 0.001) and increase of ejection fraction (17.7% +/- 4.6% to 23.7% +/- 8.8%, p < 0.001). Right-sided heart catheterization demonstrated improvement of stroke index (24.3 +/- 7.7 ml/m2 to 28.3 +/- 7.6 ml/m2, p < 0.01) and decrease of pulmonary wedge pressure (23.2 +/- 8.8 mm Hg to 17 +/- 7 mm Hg, p < 0.01). Similar results were documented at 6 and 12 months of follow-up. Functional class improved from 3.6 +/- 0.5 to 1.4 +/- 0.6 (p < 0.001). However, seven patients died at midterm follow-up because of heart failure progression or arrhythmia-related events, and survival rate was 59.2% +/- 9.4% from 6 to 24 months of follow-up. CONCLUSIONS: Partial left ventriculectomy performed with preservation of the mitral valve improves left ventricular function and congestive heart failure in patients with dilated cardiomyopathy. Nevertheless, the high incidences of heart failure progression and arrhythmia-related deaths observed after this procedure preclude its wide clinical application.

Cardiomyopathy, Dilated↗
PubMed1997

Clinical outcome after left ventricular surgical remodeling in patients with idiopathic dilated cardiomyopathy referred for heart transplantation: short-term results.

BACKGROUND: Left ventricular partial ventriculectomy (LVPV), an unconventional operation to reverse some aspects of the cardiac remodeling, has been proposed for treatment of congestive heart failure. METHODS AND RESULTS: Twenty-four patients (age 46+/-9 years) referred to heart transplantation underwent isolated LVPV or LVPV associated to valve annuloplasty. Patients were in New York Heart Association functional class IV (15) or III (9) due to idiopathic dilated cardiomyopathy. Functional class, left and right ventricular ejection fraction (radionuclide), left ventricular end-diastolic and end-systolic diameter, and fractional shortening (by echocardiography), and hemodynamic variables were determined. The mean follow-up was 474+/-174 days. Survival at 30, 180, and 365 days was 92+/-6%, 67+/-10%, and 63+/-10%, respectively. Nine patients died, and the cause was associated with arrhythmias in 4 patients. The left ventricular end-diastolic diameters before and at 23+/-14 days, 188+/-27, and 365+/-14.8 days of follow-up were 82.6+/-9.8, 68.9+/-7.8, 69.9+/-6.9, and 70+/-5.3 mm, respectively (P=0.0001). The left ventricular end-systolic diameters were 73.5+/-7.4, 55.9+/-7.5, 57.4+/-7.8, and 55+/-5.5 mm (P=.0001). Fractional shortenings were 13+/-3, 19+/-4, 18+/-5, and 22+/-2%, respectively (P=.0001). The left ventricular ejection fractions before and 18+/-14, 188+/-26, and 369+/-3.6 days after the surgery were 17.2+/-4.7, 24.5+/-8.3, 24.5+/-7.4, and 23.7+/-6.1%, respectively (P=.004). The right ventricular ejection fractions were 20.5+/-6.2, 27.9+/-8.4, 28.2+/-10.1, and 27.4+/-7.3% (P=0.02). Pressures were unchanged. There was improvement in cardiac index from 2.11+/-0.52 to 2.53+/-0.64 L/min (P=.0037). Norepinephrine blood levels reduced from 702+/-258 to 439+/-307 pg/mL (P=.001). Most surviving patients presented improvement in functional class. Sustained ventricular tachycardias were observed in 9 patients (38%). CONCLUSIONS: The left ventricular partial ventriculectomy may improve the left and right ventricular function, functional class, and cardiac output. These initial results were associated to high prevalence of sustained ventricular tachycardia. The ventriculectomy introduces the concept that reduction of left ventricular chamber diameter may improve cardiac function in heart failure. Further progress is necessary to improve the results and evaluate its proper role in the management of heart failure.

Adult↗
PubMed1997

Respiratory mechanics and morphometric changes during pneumoperitoneum in normal rats.

Pneumoperitoneum may give rise to several respiratory changes; nevertheless, no comprehensive analysis of respiratory mechanics has been performed under this condition. Respiratory mechanics and thoracoabdominal morphometry were evaluated in six sedated, anaesthetized, paralysed, and mechanically-ventilated rats before (control) and during pneumoperitoneum. After airway occlusion at end-inspiration, respiratory system, pulmonary, and chest wall resistive pressures (deltaP1,rs, deltaP1,L and deltaP1,cw, respectively) and viscoelastic/inhomogeneous pressures (deltaP2,rs, deltaP2,L and deltaP2,cw, respectively) were determined. Total pressure changes (deltaPtot) were calculated as the sum of deltaP1 and deltaP2, yielding the values of deltaPtot,rs, deltaPtot,L and deltaPtot,cw, respectively. Respiratory system, lung, and chest wall static (Est,rs, Est,L and Est,cw, respectively), and dynamic elastances (Edyn,rs, Edyn,L and Edyn,cw, respectively), and the corresponding changes in elastance (deltaE) (calculated as Edyn-Est) were also obtained. Chest wall configuration both at functional residual capacity (FRC) and end-inspiration (FRC + tidal volume (VT)) was also evaluated in another four rats. Pneumoperitoneum significantly increased deltaPtot,rs, deltaPtot,cw, deltaP2,rs, deltaP2,cw, deltaErs, deltaEcw, Est,rs, Est,L and Est,cw. Lateral and anteroposterior diameters increased significantly, with the exception of lateral diameters at the level of crista iliaca. Cephalocaudal diameter and FRC decreased. In conclusion, pneumoperitoneum augments elastances and increases the pressure dissipated against viscoelasticity/inhomogeneity of the respiratory system and chest wall. These changes are related to a cephalad displacement of the diaphragm plus changes in thoracoabdominal configuration.

Animals↗
PubMed1997

Evolution of circadian organization in vertebrates.

Circadian organization means the way in which the entire circadian system above the cellular level is put together physically and the principles and rules that determine the interactions among its component parts which produce overt rhythms of physiology and behavior. Understanding this organization and its evolution is of practical importance as well as of basic interest. The first major problem that we face is the difficulty of making sense of the apparently great diversity that we observe in circadian organization of diverse vertebrates. Some of this diversity falls neatly into place along phylogenetic lines leading to firm generalizations: i) in all vertebrates there is a "circadian axis" consisting of the retinas, the pineal gland and the suprachiasmatic nucleus (SCN), ii) in many non-mammalian vertebrates of all classes (but not in any mammals) the pineal gland is both a photoreceptor and a circadian oscillator, and iii) in all non-mammalian vertebrates (but not in any mammals) there are extraretinal (and extrapineal) circadian photoreceptors. An interesting explanation of some of these facts, especially the differences between mammals and other vertebrates, can be constructed on the assumption that early in their evolution mammals passed through a "nocturnal bottleneck". On the other hand, a good deal of the diversity among the circadian systems of vertebrates does not fall neatly into place along phylogenetic lines. In the present review we will consider how we might better understand such "phylogenetically incoherent" diversity and what sorts of new information may help to further our understanding of the evolution of circadian organization in vertebrates.

Animals↗