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Biomedical subjects

R Samson

Publications and source records attributed to R Samson.

At least 19 recordsLinked to original sources
PubMed1993

Construction and application of chromosomally integrated lac-lux gene markers to monitor the fate of a 2,4-dichlorophenoxyacetic acid-degrading bacterium in contaminated soils.

A reporter gene system, containing luxAB and lacZY, was constructed and integrated, using Tn7 transposition, into the chromosome of a 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading soil bacterium, Pseudomonas cepacia (BRI6001), to monitor its fate when introduced into soil microcosms. The genes were stably maintained in the modified strain of BRI6001, BRI6001L, for more than 300 generations in the absence of selection pressure, and had no apparent effects on biochemical or physiological properties. BRI6001L was easily and rapidly identified as light-emitting blue colonies on 2,4-D medium containing XGal (5-bromo-4-chloro-indolyl-beta-D-galacto-pyranoside) in the presence of n-decanal. Survival rates of BRI6001L introduced into non-sterile soil microcosms were substrate- and contaminant-dependent. The decrease in population density was lowest in a 2,4-D-amended agricultural soil, and highest in a wood-treatment facility soil contaminated with pentachlorophenol, creosote and heavy metals. A viable cell density as low as 10 cfu g-1 was detected in soil microcosms. The biochemical and growth properties of BRI6001 and BRI6001L, and their behaviour when introduced into soil microcosms indicates that BRI6001L can be used as a reliable model to predict the fate of BRI6001 when used to bioaugment contaminated soil.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1991

Vesical tumors in patients under 25 years of age.

Behavior of transitional cell carcinoma of the bladder during the third decade of life remains a controversial subject. During the period 1980-1988, we treated 7 patients (4 male and 3 female), 25 years of age or less (mean age 19.3, range 14-25), with transitional cell carcinoma of the bladder. Until now, all patients are alive and without disease during 12-50 months after surgery. In 6 of the 7 patients, endoscopic resection was the choice treatment for superficial stage A/O. The seventh patient underwent a partial cystectomy for a B1 Jewet stage cell carcinoma. We conclude that transitional cell carcinoma of the bladder in patients under 25 years of age has a less aggressive biological behavior. Therefore, ultrasonographic examinations and serial urine cytology represent the elective test for follow-up. Cystoscopy would only be performed in doubtful cases.

Adolescent↗
PubMed1991

[Protein and enzymatic criteria for the characterization of phytopathogenic Pseudomonas fluorescens].

Polyacrylamide gel electrophoresis of proteins was carried out to characterize eight bacterial strains belonging to the genus Pseudomonas. The sampling included three species (P. cichorii, P. viridiflava and P. syringae), with three pathovars for this last species (pv. pisi, pv. syringae, pv. tomato). Several molecular markers were evaluated: native proteins, denatured proteins, esterases, superoxide dismutases (SOD) and polyphenoloxidases (PPO). Each species or pathovar of Pseudomonas was clearly differentiated by esterase patterns. SOD, PPO and native protein patterns allowed strains of P. cichorii, P. viridiflava and P.s. pv. tomato also to be distinguished. Strains of P.s. pv. pisi and P.s. pv. syringae were identical for these criteria. Denatured protein patterns of these two pathovars and P. viridiflava were similar.

Esterases↗
PubMed1990

Effect of soil/contaminant interactions on the biodegradation of naphthalene in flooded soil under denitrifying conditions.

The mineralization of 14C-labelled naphthalene was studied in pristine and oil-contaminated soil slurry (30% solids) under denitrifying conditions using a range of concentrations from below to above the aqueous phase saturation level. Results from sorption-desorption experiments indicated that naphthalene desorption was highly irreversible and decreased with an increase in the soil organic content, thus influencing the availability for microbial consumption. Under denitrifying conditions, the mineralization of naphthalene to CO2 occurred in parallel with the consumption of nitrate and an increase in pH from 7.0 to 8.6. When the initial substrate concentration was 50 ppm (i.e. close to the aqueous phase saturation level), about 90% of the total naphthalene was mineralized within 50 days, and a maximum mineralization rate of 1.3 ppm day-1 was achieved after a lag period of approx. 18 days. When added at concentrations higher than the aqueous phase saturation level (200 and 500 ppm), similar mineralization rates (1.8 ppm day-1) occurred until about 50 ppm of the naphthalene was mineralized. After that the mineralization rates decreased logarithmically to a minimum of 0.24 ppm day-1 for the rest of the 160 days of the experiments. For both of these higher concentrations, the reaction kinetics were independent of the concentration, indicating that desorption of the substrate governs the mineralization rate. Other results indicated that pre-exposure of soil to oil contamination did not improve the degradation rates nor reduce the lag periods. This study clearly shows the potential of denitrifying conditions for the biodegradation of low molecular weight PAHs.

Biodegradation, Environmental↗
PubMed1990

Thermodynamic evidence of trophic microniches in methanogenic granular sludge-bed reactors.

The Gibbs free energy changes in methanogenic granular biomass from sludge-bed reactors were evaluated using the in situ concentrations and partial pressures of metabolites during the metabolism of acetate, hydrogen, formate and propionate. Based on mass balance calculations it appeared that the degradation of propionate into acetate, hydrogen and bicarbonate was endergonic, even if propionate was effectively degraded. On the other hand, the methane-producing reactions, both from acetate and from hydrogen plus bicarbonate, were found to be exergonic and the free energy change was sufficient for the formation of ATP. Formate was detected in only one of the two reactors. When formate, instead of hydrogen, was considered as the electron carrier between propionate-degrading and methanogenic bacteria, similar thermodynamic results were obtained. The existence of trophic microniches in the granular biomass is suggested to explain propionate degradation even though the Gibbs free energy change in the liquid surrounding the granules was positive. Hence, to make propionate degradation exergonic the dissolved hydrogen concentration surrounding the propionate-degrading bacteria would have to be about 30 times lower than in the free liquid.

Anaerobiosis↗
PubMed1990

Influence of environmental factors on 2,4-dichlorophenoxyacetic acid degradation by Pseudomonas cepacia isolated from peat.

A Pseudomonas cepacia, designated strain BRI6001, was isolated from peat by enrichment culture using 2,4-dichlorophenoxyacetic acid (2,4-D) as the sole carbon source. BRI6001 grew at up to 13 mM 2,4-D, and degraded 1 mM 2,4-D at an average starting population density as low as 1.5 cells/ml. Degradation was optimal at acidic pH, but could also be inhibited at low pH, associated with chloride release from the substrate, and the limited buffering capacity of the growth medium. The only metabolite detected during growth on 2,4-D was 2,4-dichlorophenol (2,4-DCP), and degradation of the aromatic nucleus was by intradiol cleavage. Growth lag times prior to the on-set of degradation, and the total time required for degradation, were linearly related to the starting population density and the initial 2,4-D concentration. BRI6001, grown on 2,4-D, oxidized a variety of structurally similar chlorinated aromatic compounds accompanied by stoichiometric chloride release.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1989

Does the addition of albumin to the prime solution in cardiopulmonary bypass affect clinical outcome? A prospective randomized study.

Colloid solution is commonly used to increase the oncotic pressures of priming solutions used in the cardiopulmonary bypass circuit. To study the effectiveness of this practice, we prospectively randomized 100 adult patients undergoing cardiac operations to receive Ringer's lactate solution plus 50 gm of albumin (group A) or Ringer's lactate solution alone (group B) as the prime solution for the bypass circuit. Personnel involved in the management of these patients were blinded concerning the group to which the patients had been randomized. Forty clinical parameters related to perioperative fluid balance, cardiopulmonary function, and renal function were studied. Although group B received a larger volume of crystalloid solution intraoperatively (p less than 0.05), had a lower mean cardiac filling pressure (p less than 0.05), and had a higher hematocrit value (p less than 0.05) in the immediate postoperative period, all mean values for both groups were within the normal range. There were no differences between the two groups with regard to postoperative clinical parameters of cardiopulmonary and renal function, nor was outcome affected by the addition of albumin to the prime solution. We conclude that there is no clinically detectable advantage for the practice of adding 50 gm of albumin to the priming solution of bypass circuits in adults undergoing cardiac operations. Routinely supplementing the bypass prime solution with albumin adds significant cost, estimated to be approximately $10,000 per 100 cases, without demonstrable clinical benefits. Whether this practice can be of value in selected cases needs to be further studied.

Albumins↗
PubMed1987

Is high potassium solution necessary for reinfusions in "multidose" cold cardioplegia? A randomized prospective study using computerized Holter system.

Multidose potassium cardioplegia is a common method of myocardial preservation. Although initial potassium arrest conserves high-energy phosphates, there is conflicting evidence that repeat high potassium boluses augment this protection. Fifty-six patients were prospectively randomized to receive multidose cold high potassium cardioplegia (27 mEq of KCl/L) both in the initial and subsequent infusions (Group 1) or an initial cold high potassium (27 mEq/L) cardioplegia followed by boluses of cold low potassium (7 mEq, of KCl/L) solution (Group 2). The two groups were compared in terms of postoperative myocardial electrical stability and hemodynamic performance. Electrocardiograms were recorded by continuous Holter monitor, and the data were analyzed by computer. The duration of aortic cross-clamping and cardiopulmonary bypass did not differ between groups. Group 1, who received more total KCl than Group 2 (p less than .005), experienced more high-grade ventricular ectopia during both reperfusion (p less than .001) and the immediate postoperative period (p less than .001), and required more lidocaine hydrochloride (p less than .001) for arrhythmias. There was no significant difference in hemodynamic performance between the two groups. This study fails to show an advantage to multidose "high potassium" cardioplegia and found a significant increase in ventricular ectopia associated with its use. We advocate using low potassium solutions after initial cold high potassium arrest.

Adult↗
PubMed1984

Complement (C3, C4) consumption in cardiopulmonary bypass, cardioplegia, and protamine administration.

Anaphylatoxins produced by complement activation have been postulated to be responsible for postperfusion syndrome and protamine hypotension in patients undergoing cardiac surgical procedures. The consumption of serum complement components C3 and C4, which reflects the classic and alternate pathway activations of the complement system, was studied in 22 patients undergoing cardiac operations. Prior to the onset of cardiopulmonary bypass, the complement levels were within normal range. Rapid reduction in both C3 and C4 within minutes of cardiopulmonary bypass indicated rapid complement activation. Such a reduction in complement levels could not be accounted for by either hemodilution or transfusion of complement-poor blood. Aortic cross-clamping and cold potassium cardioplegia followed by myocardial reperfusion did not lead to further consumption of C3 and C4. Slow intravenous infusion of protamine sulfate after cardiopulmonary bypass did not change C3 and C4 levels significantly in our patients, although protamine and heparin-protamine complex have been shown to activate complement components in vitro. In another group of 9 similar cardiac surgical patients, C3 and C4 were found to return to normal levels within 24 hours after operation. This study thus confirms the rapid activation of the complement system by cardiopulmonary bypass but fails to demonstrate further activation of the complement system by cardioplegia or protamine administration.

Adult↗
PubMed1980

Traumatic arterial spasm--rarity or nonentity.

Despite numerous opinions in literature questioning the existence of traumatic arterial spasm we believe that, although infrequent, the condition nevertheless occurs. A survey of the vascular literature on this subject appears to support this view. Spasm, when found, should be treated by resection of the arterial segment and its replacement with an appropriate graft unless spasm is relieved by vasodilation.

Adolescent↗
PubMed1979

Current status of surgery of the omentum.

The greater omentum is a unique organ with multipotential properties. A simple procedure converts it into a vascularized pedicle that may be utilized throughout the body. Knowledge of the possible applications of free or pedicled omental grafts will significantly add to the armamentarium of a clinical and experimental surgeon.

Digestive System Surgical Procedures↗
PubMed1979

Fungal infection of a vascular prosthesis.

Chronic debilitating hematological disorders and cytotoxic drugs may create conditions causing a predisposition to fungal infections of vascular grafts. Under such circumstances routine bacteriological investigations should be supplemented by specific fungal media cultures and microscopic examination of removed infected graft.

Aged↗
PubMed1976

Carcinoembryonic antigen in colorectal practice: report of three cases.

CEA, in combination with the time-honored barium enema, sigmoidoscopy, rectal examination with guaiac determinations, and thorough clinical history, is a useful tool for the colorectal surgeon in following the progression of disease in both colorectal carcinoma patients and patients who have certain premalignant conditions. In this high-risk group of patients, CEA determinations as well as colonoscopy are becoming increasingly useful. That tumors on the left side are associated with higher CEA levels than those on the right side, due to vascular invasion or the grades of the tumors, and that often CEA antigenicity and severity of symptoms in ulcerative colitis correlate well, are emphasized. Finally, following total colectomy in five cases of ulcerative colitis, all CEA titers decreased to the normal range and have remained there.

Adult↗