Biomedical subjects

P Gerard

Publications and source records attributed to P Gerard.

At least 19 recordsLinked to original sources

PubMed2006

[Surgical left ventricular remodelling via endoventriculoplasty: clinical observation].

A case of dilated ischemic cardiomyopathy, with severely impaired left ventricular systolic function, treated by endoventriculoplasty and CABG, is reported. The authors discuss the modern concepts regarding the surgical treatment of large anterior asynergic scars following occlusion of the LAD. Since there are more similarities between akinesia and dyskinesia than previously thought, the endoventriculoplasty of DOR may constitute a new way to surgically remodel the left ventricle in dilated cardiomyopathies with large anterior akinesia. This surgery significantly improves the ventricular function and the overall patients' prognosis at short and mid term follow up.

Cardiomyopathy, Dilated↗

PubMed2005

Computed tomographic pulmonary angiography and prognostic significance in patients with acute pulmonary embolism.

BACKGROUND: Patients with acute pulmonary embolism (APE) present with a broad spectrum of prognoses. Computed tomographic pulmonary angiography (CTPA) has progressively been established as a first line test in the APE diagnostic algorithm, but estimation of short term prognosis by this method remains to be explored. METHODS: Eighty two patients admitted with APE were divided into three groups according to their clinical presentation: pulmonary infarction (n = 21), prominent dyspnoea (n = 29), and circulatory failure (n = 32). CTPA studies included assessment of both pulmonary obstruction index and right heart overload. Haemodynamic evaluation was based on systolic aortic blood pressure, heart rate, and systolic pulmonary arterial pressure obtained non-invasively by echocardiography at the time of diagnosis of pulmonary embolism. RESULTS: The mortality rate was 0%, 13.8% and 25% in the three groups, respectively. Neither the pulmonary obstruction index nor the pulmonary artery pressure could predict patient outcome. In contrast, a significant correlation with mortality was found using the systolic blood pressure (p<0.001) and heart rate (p<0.05), as well as from imaging parameters including right to left ventricle minor axis ratio (p<0.005), proximal superior vena cava diameter (p<0.001), azygos vein diameter (p<0.001), and presence of contrast regurgitation into the inferior vena cava (p = 0.001). Analysis from logistic regression aimed at testing for mortality prediction revealed true reclassification of 89% using radiological variables. CONCLUSION: These results suggest that CTPA quantification of right ventricular strain is an accurate predictor of in-hospital death related to pulmonary embolism.

Acute Disease↗

PubMed2005

Defective remethylation of homocysteine is related to decreased synthesis of coenzymes B2 in thyroidectomized rats.

We investigated the influence of hypothyroidism on homocysteine metabolism in rats, focusing on a hypothetical deficient synthesis of FAD by riboflavin kinases. Animals were allocated in control group (n = 7), thyroidectomized rats (n = 6), rats with diet deficient in vitamin B2, B9, B12, choline and methionine (n = 7), thyroidectomized rats with deficient diet (n = 9). Homocysteine was decreased in operated rats (2.6 +/- 1.01 vs. 4.05 +/- 1.0 mumol/L, P = 0.02) and increased in deficient diet rats (29.56 +/- 4.52 vs. 4.05 +/- 1.0 micromol/L, P = 0.001), when compared to control group. Erythrocyte-Glutathione-Reductase-Activation-Coefficient (index of FAD deficiency) was increased in thyroidectomized or deficient diet rats (P = 0.004 for both). Methylenetetrahydrofolate-reductase and methionine-synthase activities were decreased in thyroidectomized rats but not in those subjected to deficient diet. Cystathionine-beta-synthase was increased only in operated rats. Taken together, these results showed a defective re-methylation in surgical hypothyroidism, which was due in part to a defective synthesis of vitamin B2 coenzymes. This defective pathway was overcompensated by the increased Cystathionine-beta-synthase activity.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗

PubMed2003

Brown Norway rat ovalbumin-specific immunoglobulin E antibodies increase the human basophil expression of CD63 marker.

Anaphylactic shock is an immunoglobulin E (IgE)-dependent hypersensitivity. Biological tests like leucocyte histamine release (LHR) and human basophil activation (HBA), frequently used in human allergy, reflect both the amount of IgE fixed on cells and the cellular reactivity. To assess whether serum-specific IgE from Brown Norway (BN) rats prepared for ovalbumin (OVA)-induced anaphylactic shocks can activate human basophils which has a potential interest in experimental allergy: such a test could rapidly assert an IgE sensitization in laboratory animals genetically T-helper 2 (Th2)-predisposed. Rats (n = 39) were immunized three times (day 0, day 5 and day 21) with OVA injected subcutaneously. One week after the third immunization, a shock was induced with an intravenous (i.v.) bolus of OVA. Sensitization was assessed by passive cutaneous anaphylaxis (PCA) test and dosages of serum IgE antibodies anti-OVA by enzyme-linked immunosorbent assay. Blood basophils were counted before and during the shock. Before the shock induction (at day 21), an LHR test was performed on rat blood, and human basophils were sensitized with rat sera. HBA was demonstrated by the increase in the percentage of cells expressing CD63 antigen membrane, measured by flow cytometry. Twenty-one days after the first subcutaneous (s.c.) immunization, the rat serum induced a significant HBA. HBA was observed neither with the same serum previously heated nor with the serum from nonimmunized rats (NIRs). OVA-specific IgEs were significantly increased in immunized rat (IR) serum. The PCA test was negative when the serum was previously heated (56 degrees C). We never observed any circulating basophils, and LHR test was negative. After OVA i.v. administration, all IRs died rapidly. HBA testing strongly suggests a mediation by specific IgE in the increase of CD63 in BN rats. Thus, HBA test seems useful in assessing whether an experimental allergy was induced in animals genetically predisposed to an immune response, Th2-mediated, like BN rat. We also conclude that rat basophil activation does not participate in the histamine release during anaphylactic shock in sensitized BN rats.

Anaphylaxis↗

PubMed2003

Alteration of left ventriculo-arterial coupling and mechanical efficiency during acute myocardial ischemia.

AIM: Myocardial revascularisation being frequently performed during acute myocardial ischemia, in a hostile hemodynamic environment, we evaluated left ventriculo-arterial (VA) coupling, left ventricular (LV) mechanical efficiency, and the mechanical properties of the systemic vasculature during acute myocardial ischemia. METHODS: In 6 pigs, vascular properties [characteristic impedance (R(1)), peripheral resistance (R(2)), compliance (C), inductance (L), arterial elastance (E(a))] were estimated with a windkessel model. LV function was assessed by the slope (E(es)) of end-systolic pressure-volume relationship (ESPVR), and stroke work (SW) - end-diastolic volume (EDV) relation. Pressure-volume area (PVA) was referred to as myocardial oxygen consumption. VA coupling was defined as E(es)/E(a), and mechanical efficiency as SW/PVA. After baseline recordings, the left anterior descending coronary artery was ligated and hemodynamic measures obtained every 30 minutes for 3 hours. Data are expressed as mean (SEM). RESULTS: Coronary occlusion induced an ESPVR rightward shift, and decreased E(es) from 3.67 (0.33) to 1.92 (0.20) mmHg/ml and the slope of the SW - EDV relationship from 72.3 (3.4) to 40.4 (4.5) mmHg (p<0.001), while E(a) increased from 3.33 (0.56) to 4.65 (0.29) mmHg/ml (p<0.005). This was responsible for a dramatic alteration of VA coupling from 1.22 (0.11) to 0.44 (0.07), (p<0.001). While R2 increased from 1.72 (0.30) to 2.38 (0.16) mmHg x s x ml(-1) (p<0.05) and C decreased from 0.78 (0.16) to 0.46 (0.08) ml/mmHg (p<0.05), R(1) and L were unchanged. Coronary occlusion decreased SW from 4056 (223) to 2580 (122) mmHg.ml (p<0.001), while PVA and SW/PVA decreased from 5575 (514) to 4813 (317) mmHg x ml (NS), and from 0.76 (0.04) to 0.57 (0.03) (p<0.001), respectively. CONCLUSION: Acute myocardial ischemia severely altered left ventriculo-arterial coupling and LV mechanical efficiency. Impaired left VA coupling was due to a combination of augmented arterial elastance, secondary to early vasoconstriction later associated with decreased arterial compliance, and decreased LV contractility.

Animals↗

PubMed2001

Cardiac surgery in octogenarians; peri-operative outcome and long-term results.

AIMS: Because the elderly are increasingly referred for operation, we reviewed the results of cardiac surgery in patients of 80 years or older. METHODS AND RESULTS: Records of 182 consecutive octogenarians who had had cardiac operations between 1992 and 1998 were reviewed. Follow-up was 100% complete. Seventy patients had coronary grafting (CABG), 70 aortic valve replacement, 30 aortic valve replacement+CABG, and 12 mitral valve repair/replacement. Rates of hospital death, stroke, and prolonged stay (>14 days) were as follows: CABG: 7 (10%), 2 (2.8%) and 41 (58%); aortic valve replacement: 6 (8.5%), 2 (2.8%) and 32 (45.7%); aortic valve replacement+CABG: 8 (26.5%), 1 (3.8%) and 14 (46.6%); mitral valve repair/replacement: 3 (25%), 1 (8.3%) and 5 (41.6%). Multivariate predictors (P<0.05) of hospital death were New York Heart Association functional class, urgent procedure, prolonged cardiopulmonary bypass time, and, after aortic valve replacement, previous percutaneous aortic valvuloplasty. Ascending aortic atheromatous disease was predictive of stroke, while pre-operative myocardial infarction was predictive of prolonged hospital stay. Actuarial 5-year survival was as follows: CABG, 65.8+/-8.8%; aortic valve replacement, 63.6+/-7.1%; aortic valve replacement+CABG, 62.4+/-6.8%; mitral valve repair/replacement, 57.1+/-5.6%; and total, 63.0+/-5.6%. Multivariate predictors of late death were pre-operative myocardial infarction, and urgent procedure. Ninety percent of long-term survivors were in New York Heart Association class I or II, and 87% believed having a heart operation after age 80 years was a good choice. CONCLUSION: Cardiac operations are successful in most octogenarians with increased hospital mortality, and longer hospital stay. Long-term survival and quality of life are good.

Aged↗

PubMed2000

Radiology in the diagnosis and therapy of gastrointestinal bleeding.

Major breakthroughs in catheter and guidewire design as well as improvements in angiographic x-ray equipment currently allow interventional radiologists to diagnose massive life-threatening upper and lower GI hemorrhage and to stop the bleeding safely and effectively using superselective catheterization and microcoil embolization. For chronic or recurrent GI bleeding, when endoscopy is unrevealing or equivocal, barium studies, CT scanning, nuclear medicine studies, and angiography can help determine the cause of bleeding. A multidisciplinary approach, including the gastroenterologist, radiologist, and surgeon, is extremely helpful in managing GI bleeding, particularly in high-risk patients or patients presenting as diagnostic dilemmas.

Angiography↗

PubMed2000

Increased aortic compliance maintains left ventricular performance at lower energetic cost.

OBJECTIVE: The aim of this study was to investigate left ventricular contractility and energetic cost of cardiac ejection under conditions of acute increase in aortic compliance. METHODS: In six anaesthetized pigs, ascending aortic compliance was increased by adding a volume chamber in parallel to the ascending aorta. Systemic vascular parameters, including characteristic impedance, peripheral resistance, total vascular compliance, and inertance, were estimated with a four-element windkessel model. Arterial elastance was derived from these parameters. Left ventricular systolic function was assessed by end-systolic pressure-volume relationship (end-systolic elastance), and stroke work. Pressure-volume area was used as a measure of myocardial oxygen consumption. Heart rate remained constant during the experimentation. RESULTS: Adding the aortic volume chamber significantly increased vascular compliance from 0. 95+/-0.08 to 1.17+/-0.06 ml/mmHg (P<0.01), while inductance, characteristic impedance, peripheral resistance, and arterial elastance remained statistically at basal values, respectively 0. 0020+/-0.0003 mmHg.s(2)/ml, 0.105+/-0.009 mmHg.s/ml, 1.27+/-0.12 mmHg.s/ml, and 2.43+/-0.21 mmHg/ml. During the same interval, stroke work and pressure-volume area decreased respectively from 2700+/-242 to 2256+/-75 mmHg.ml (P<0.01), and from 3806+/-427 to 3179+/-167 mmHg.ml (P<0.01). Stroke work and pressure-volume area decreased at matched end-diastolic volumes. In contrast, end-systolic elastance, ejection fraction, and stroke volume remained statistically unchanged, respectively at 2.29+/-0.14 mmHg/ml, 48.1+/-2.1 %, and 32. 4+/-1.7 ml. CONCLUSIONS: These data suggest that, when facing an increased aortic compliance, the left ventricle displays unchanged contractility, but the energetic cost of cardiac ejection is significantly decreased. These data may be of clinical importance when choosing an artificial prosthesis for ascending aortic replacement.

Animals↗

PubMed2000

Early stage results after oesophageal resection for malignancy - colon interposition vs. gastric pull-up.

OBJECTIVE: The aims of our study were to determine if using the colon as a digestive transplant after oesophagectomy for cancer was associated with increased postoperative complications, and to assess the impact of preoperative radiochemotherapy on postoperative hospital outcome. METHODS: From January 1990 to December 1998, 130 patients underwent oesophageal resection for malignancy. There were 103 males and 27 females (age: 61.3+/-11.5 years). Indications were squamous cell carcinoma in 69 patients and adenocarcinoma in 61. Preoperatively 30 patients (eight in stage IIB, 18 in stage III, and four in stage IV) received radiochemotherapy. There were 84 subtotal oesophagectomies, with anastomosis in the neck in 44 patients and at the thoracic inlet in 40, and 46 distal oesophageal resections. Digestive continuity was restored with the stomach in 92 patients (age: 63.4+/-10.2 years) and the colon in 38 (age: 52.3+/-12.8 years). With the exception of age (P<0.0001), there was no significant preoperative difference between gastric and colonic groups. RESULTS: Hospital mortality was 8.5% (11 patients), decreasing from 18.5% (before 1993) to 3.8% (since 1993). One patient (2.5%) died in the colonic graft group and ten (11%) in the gastric pull-up group (P=0.17). Postoperative complications occurred in 40 patients (31%), respectively, in ten (26%) and 30 (33%) patients after colonic and gastric transplants (P=0.48), and were pulmonary insufficiency or infection in 29 patients, anastomotic fistula in six, myocardial infarction in five, recurrent nerve palsy in four, renal insufficiency in three, and cerebrovascular accident in one. All fistulas occurred in the gastric pull-up group. The incidence of postoperative pulmonary complications was 70% (21/30 patients) in the subgroup who received preoperative radiochemotherapy, as compared to 11% (5/44 patients) in the subgroup of comparable staging, but without preoperative treatment (P<0.001). CONCLUSIONS: Colonic grafts are not associated with increased postoperative mortality or complications. Our results suggest that preoperative neoadjuvant treatment significantly increases postoperative pulmonary complications.

Adenocarcinoma↗

PubMed2000

Heart rate variability and the outcome of head-up tilt in syncopal children.

OBJECTIVE: This study evaluated autonomic nervous system function in 5 young (6-10 years old) and 5 older (10-15 years) children with recurrent episodes of neurally mediated syncope and a positive tilt-test result, 10 with syncope but a negative test result and 30 age-matched healthy volunteers. METHODS: Time- (SDNN, SDNNi, SDANNi, rMSSD, pNN50) and frequency-domain indices (LF, HF, LF/HF) of heart rate variability (HRV) were measured during a 24-hour Holter recording and for 5 min. segments before and during 90 degrees head-up tilt (tests lasted 30 min. or until syncope occurred). RESULTS: 24-hour HRV-indices were within the normal range for all syncopal patients. Mean RR interval and HRV-indices, except LF/HF, were higher in the older children with a positive test result before they were tilted and during the first 5 min. of head-up tilt. HRV-indices tended to be lower after tilt in the younger children with a positive test result. SDNN and LF in older children with a positive test result and LF/HF in the younger ones increased during the 5 min preceding the syncope. No difference was observed between syncopal children with a negative test result and controls. CONCLUSION: This study confirms that patients with vasovagal syncope have no chronic differences from normal subjects in autonomic nervous system activity. The modulation of the autonomic tone during head-up tilt is abnormal in children who faint during the test, but younger and older patients respond differently to the orthostatic stimulus.

Adolescent↗

PubMed1999

Analysis of endotoxin effects on the intact pulmonary circulation.

OBJECTIVE: The mechanism of sustained alterations in pulmonary hemodynamics during endotoxin shock remains unclear. To gain more detailed knowledge we used the four-element windkessel model as a descriptor of the pulmonary circuit. METHODS: Consecutive changes in characteristic resistance (R1), vascular compliance (C), input resistance (R2) and inductance (L) were continuously assessed following injection of endotoxin in 6 anaesthetised pigs, and were compared with the corresponding values measured in a similar group of sham-operated animals. RESULTS: Endotoxin challenge resulted in a biphasic pulmonary artery pressure response. Blood flow decreased progressively from 2.8 +/- 0.2 l/min to 2 +/- 0.2 l/min. Ohmic pulmonary vascular resistance (PVR) increased gradually from 0.2 +/- 0.04 to 0.76 +/- 0.1 mm Hg s ml-1. The early increase in PAP (from 14 +/- 2 to 27 +/- 4 mm Hg) was mediated by changes in both R1 (from 0.04 +/- 0.01 to 0.06 +/- 0.01 mm Hg s ml-1) and R2 (from 0.16 +/- 0.04 to 0.61 +/- 0.2 mm Hg s ml-1). These responses, in turn, altered the proximal vascular compliance. A subsequent increase in PAP (from 27 +/- 2 to 32 +/- 3 mm Hg) paralleled the specific decline in distal pulmonary vasculature compliance from 0.84 +/- 0.1 to 0.65 +/- 0.1 ml/mmHg. Analysis of the time course of PVR did not allow us to distinguish between vasoconstriction and stiffening of the vascular tree as mechanisms accounting for PAP changes. CONCLUSIONS: Endotoxemia leads to pulmonary hypertension, which is a result of constriction of proximal pulmonary arteries during the early phase, whereas the late phase is characterised by a decline in distal pulmonary vasculature compliance.

Animals↗

PubMed1999

Aortic valve replacement in the octogenarians: perioperative outcome and clinical follow-up.

OBJECTIVES: To determine long-term results of aortic valve replacement (AVR) in patients 80 years old or older, and assess the factors influencing perioperative outcome. METHODS: Data were reviewed on 83 consecutive octogenarians, undergoing aortic valve replacement between 1992 and 1997. There were 66 women and 17 men (mean age: 82.8 years). Fifty-seven patients (69%) were in New York Heart Association (NYHA) class III-IV and six had previous myocardial infarction. Three patients had previous percutaneous aortic valvuloplasty. There were 19 urgent procedures (23%). Coronary artery bypass grafting (CABG) was performed on 21 patients (25%). Possible influence of preoperative and operative variables on early and late mortality was performed with univariate and multivariate statistical analysis, and survival was estimated with the Kaplan-Meier method. RESULTS: Operative mortality was 13% (9% for AVR, 24% for AVR-CABG). Postoperative complications were respiratory failure in 19 patients, atrial fibrillation in 19, hemodialysis in four, myocardial infarction in four and stroke in two patients. Five patients required pacemaker insertion for permanent atrioventricular block. Median hospital stay and intensive care unit stay were 19.8 +/- 12.2 days and 7.9 +/- 3.4 days, respectively. Multivariate predictors of hospital death (P < 0.05) were percutaneous aortic valvuloplasty, NYHA class IV, and urgent procedure. Mean follow-up was 26.5 months. Survival at 1, 2, and 5 years was 98.5 +/- 1.4% (63 patients at risk), 93.4 +/- 3.2% (47 patients at risk), and 78.2 +/- 6.9% (six patients at risk), respectively. Preoperative myocardial infarction and urgent procedure were independent predictors of late death. At most recent follow-up, 91% were angina free and 81% were in class I-II. CONCLUSIONS: Aortic valve replacement in octogenarians can be performed with acceptable mortality. These results stress the importance of early operation on elderly patients with aortic valve disease. Both long-term survival and functional recovery are excellent.

Aged↗

PubMed1999

Human haptocorrin in hepatocellular carcinoma.

This study aimed to determine whether haptocorrin (HC), a vitamin B12 binder, is stored in hepatic cells and whether this storage is modified by hepatic carcinogenesis. It was carried out using immunohistochemistry on different liver tissues (normal liver and steatosis, N = 22; cirrhosis, N = 13; and hepatocellular carcinoma, N = 31). No significant immunostaining of HC was detected in noncancerous biopsies with the exception of in one case of cirrhosis. Hepatocellular carcinoma (HCC) sections showed a weak to moderate cytoplasmic staining of cancerous cells (93% of cases) and of noncancerous hepatocytes surrounding the tumor (95%) of cases. Sections with pseudoglandular structures showed a moderate to strong staining of their secretion products. These results and previous studies would seem to confirm the hypothesis that the raised HC serum level observed in HCC is due both to the increased hepatic synthesis of HC and to a decreased uptake by the liver of the particular isoform of this glycoprotein present in the serum of HCC patients.

Biomarkers↗

PubMed1999

Assimilation of [57Co]-labeled cobalamin in human fetal gastrointestinal xenografts into nude mice.

Cobalamin (Cbl) and its Cbl-binding proteins are present in amniotic fluid. Because amniotic fluid is swallowed by the embryo-fetus, we studied the ability of Cbl to be transported and metabolized across the embryo-fetal digestive tract. Human embryonic stomachs and intestines were transplanted into nude mice. The basal secretion of Cbl-binding proteins was studied by gel filtration of the graft juices. Intrinsic factor (IF) was looked for in gastric mucosa by immunohistochemistry. The uptake of [57Co]-labeled Cbl by the intestinal graft was studied by Schilling tests and HPLC. IF, haptocorrin, and a transcobalamin-like protein were detected in gastric juice, with concentration ranges of 5.0-26.4, 1.9-27.1, and 5.2-12.6 pmol/mL, respectively. The IF [57Co]Cbl complex had a single isoprotein with a pI at 5.6, which was maintained after incubation with neuraminidase. Urine excretion percentages (Schilling tests) ranged from 5.5 to 21.2% and from 0.3 to 1.6% when cyano-[57Co]Cbl-IF or cyano-[57Co]Cbl, respectively, was instilled in intestinal grafts. Chloroquine reduced significantly the percentage of excreted [57Co]Cbl. The [57Co]Cbl was mainly excreted as cyano-[57Co]Cbl in urines, showing a low coenzyme conversion. In conclusion, IF is secreted by the nonstimulated embryonic stomach and lacks sialic acid. Cbl binds to it and is subsequently transported across the xenografted embryo-fetal intestine. This suggests that amniotic fluid may contribute to Cbl delivery to the embryo-fetus.

Amniotic Fluid↗

PubMed1998

Pulmonary impedance and right ventricular-vascular coupling in endotoxin shock.

OBJECTIVE: We tested the hypothesis that right heart failure during endotoxin shock may result from altered ventriculovascular coupling responsible for impeding power transfer to the pulmonary circulation. METHODS: The changes in vascular pulmonary input impedance and right ventricular contractility produced by low-dose endotoxin infusion were studied in 6 intact anesthetized dogs. RESULTS: Endotoxin insult resulted in pulmonary hypertension (from 22 +/- 2 to 33 +/- 3 mmHg) associated with significant decreases in stroke volume (from 26.9 +/- 4 to 20.2 +/- 3 ml) and right ventricular ejection fraction (from 41 +/- 3 to 32 +/- 2%). The first minimum of input impedance spectrum and zero phase were shifted towards higher frequencies. Input resistance and characteristic resistance were dramatically increased. The latter change contributed to a significant increase in the pulsatile component of total right ventricular power output from 13 to 21%, indicating a reduction in the hydraulic right ventricle power output delivered into the main pulmonary artery. Overall changes in input pulmonary impedance were indicative of increased afterload facing the right ventricle leading to depressed performance. In contrast, right ventricular systolic elastance was simultaneously increased from 0.56 to 0.93 mmHg/ml indicating an increase in right heart contractility. CONCLUSION: These data suggest that pulmonary hypertension in the setting of experimental endotoxin shock is accompanied by deleterious changes in the pulmonary impedance spectrum, which are responsible for a mismatch of increased contractile state of the right ventricle to the varying hydraulic load ultimately leading to ventricular-vascular uncoupling.

Analysis of Variance↗

PubMed1998

Effect of glucose on glycerol metabolism by Clostridium butyricum DSM 5431.

The levels of 1,3-propanediol dehydrogenase and of the glycerol dehydrogenase in Clostridium butyricum grown on glucose-glycerol mixtures were similar to those found in extracts of cells grown on glycerol alone, which can explain the simultaneous glucose-glycerol consumption. On glycerol, 43% of glycerol was oxidized to organic acids to obtain energy for growth and 57% to produce 1,3-propanediol. With glucose-glycerol mixtures, glucose catabolism was used by the cells to produce energy through the acetate-butyrate production and NADH, whereas glycerol was used chiefly in the utilization of the reducing power since 92-93% of the glycerol flow was converted through the 1,3-propanediol pathway. The apparent K(m)s for the glycerol dehydrogenase was 16-fold higher for the glycerol than that for the glyceraldehyde in the case of the glyceraldehyde-3-phosphate dehydrogenase and fourfold higher for the NAD+, providing an explanation for the shift of the glycerol flow toward 1,3-propanediol when cells were grown on glucose-glycerol mixtures.

Alcohol Dehydrogenase↗

PubMed1998

Effects of PEEP on systemic venous capacitance.

The aim of the present study was to determine effects of positive end expiratory pressure (PEEP) application on peripheral venous capacitance and relate them to concomitant central hemodynamic disturbances. The venous volume-pressure (V/P) relationships were studied in 6 intact anesthetized pigs to describe the effects of PEEP on systemic venous compliance (computed as the slope of the V/P relationship) and unstressed volume (referred to as the extrapolated volume intercept). Cardiac volumes as well as partitioning of circulating blood volume between central (ITBV) and peripheral (PBV) compartments were assessed by thermo-dye dilution techniques. During a 15 cm H2O PEEP application, venous compliance was reduced by 48%, while unstressed volume was increased by 25% and peripheral blood pooling increased from 63 to 74%. As a result, left heart and right ventricular end diastolic volumes were decreased by 8% and by 44%, respectively. It is concluded that increased venous unstressed volume and reduced compliance depicted the distension of the venous tree secondary to PEEP which acted as an impediment to venous return. As a consequence, cardiac output was reduced because of decreased preload.

Animals↗

PubMed1998

Time domain method to identify simultaneously parameters of the windkessel model applied to the pulmonary circulation.

Lumped models are frequently used to provide a satisfactory description of the hemodynamic properties of the pulmonary vasculature. The purpose of this study is to describe a method to identify simultaneously the parameters values of windkessel models components. The following equation was used to obtain R1 (characteristic resistance), R2 (peripheral resistance), C (total compliance) and L (inertance): [formula: see text] where ki are the following functions of L, R1, R2 and C: [formula: see text] To assess the accuracy of the method, estimates of R1, R2, and C were compared to characteristic impedance Rc, vascular resistance PVR and pulmonary arterial compliance Cd respectively computed from referenced methods. Comparison between R1 and Rc, PVR and R1 + R2, C and Cd were obtained in 5 anaesthetised pigs during basal conditions and after endotoxin-shock. The results indicate that in both conditions, comparisons evidenced highly significant correlations between values computed by the different approaches (p < 0.0001). Although our method yielded to consistently lower values than values provided by referenced methods, the results were concordant with respect to the expected response of pulmonary vasculature to endotoxin insult. We conclude that our method of identification is suitable for the assessment of lumped parameters windkessel model estimates. The main interest is that actual resistance and compliance values can be obtained easily and simultaneously by a global method approach.

Animals↗