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Biomedical subjects

C T Lewis

Publications and source records attributed to C T Lewis.

At least 37 records · Page 2Linked to original sources
PubMed1991

Risk factors for cardiac operations in adult Jehovah's Witnesses.

During a 27-year-period, 663 adults of the Jehovah's Witness faith underwent open heart procedures at the Texas Heart Institute. To determine the effect of recent changes in operative techniques and in the patient population itself on early mortality, we reevaluated the surgical outcome in this special group of patients. We reviewed the charts of 88 consecutive Jehovah's Witness patients who had an open heart operation between January 1986 and March 1989 and compared demographic variables in this group with those of 575 patients who underwent operation between May 1963 and January 1986. In our recent series, patients were older (mean age, 61 years versus 54 years), and 16% were seen for repeat procedures. Early mortality (less than or equal to 30 days postoperatively) was lower in the recent series than in the earlier series (7.0% versus 10.7%), but the difference between the groups was not statistically significant. We identified several important factors associated with an increased risk of early death in the recent group of patients. These factors included repeat cardiac operations (p less than 0.01), especially for valvar dysfunction, severe left ventricular dysfunction (defined as an ejection fraction less than 0.35) (p less than 0.01), and a hemoglobin level lower than 80 g/L (8 g/dL) (p less than 0.01) on postoperative day 1. Although blood loss remains the leading cause of death in these patients, cardiac operations can be performed with an acceptable mortality.

Aged↗
PubMed1991

Subcutaneous fat necrosis associated with pancreatic islet cell carcinoma.

A 75-year-old man with generalized subcutaneous fat necrosis was found to have an islet cell carcinoma of the pancreas. The histologic diagnosis of islet cell carcinoma was confirmed by electron microscopy, which showed characteristic intracytoplasmic granules. This is the second report of the association of islet cell carcinoma of the pancreas with generalized subcutaneous fat necrosis.

Adenoma, Islet Cell↗
PubMed1990

Neo-intimal development on textured biomaterial surfaces during clinical use of an implantable left ventricular assist device.

Implantable left ventricular assist systems are being developed for long term clinical use. Prototype devices are currently used as extended mechanical bridges to cardiac transplantation. The Thermo Cardiosystems Inc. (TCI) pneumatic pusher plate left ventricular assist device (LVAD) features textured blood contacting surfaces to encourage the formation of an adherent fibrin-cellular coagulum. This serves as the foundation for the development of a neo-intimal lining. The TCI LVAD was implanted in 6 male patients (age range 22-53 years) between 1986 and 1988. The duration of implantation ranged from 1-41 days. No clinical thromboembolic events or pump-related thromboembolism occurred and none was evident at necropsy. The six device linings have been fully evaluated. Explanted devices were free of thrombus and calcification. Lining samples for light and electron microscopy were collected from areas of the diaphragm identical for flex and blood shear conditions and from high and low shear areas on the static housing. Islands of collagenous tissue were deposited on the static housing amongst compact fibrin. By day 13, cells populated the surface of the developing neo-intima overlying the diaphragm. By 41 days, the surface cell density increased and the cells became spindle shaped and relatively orientated in the high shear/flex area. Immunohistochemical techniques suggest that these cells are of mesenchymal origin. Textured blood contacting surfaces appear satisfactory in the preliminary clinical use of this device.

Adult↗
PubMed1990

The use of an implantable left ventricular assist device following irreversible ventricular fibrillation secondary to massive myocardial infarction.

A TCI1 rough surface left ventricular assist device (LVAD) was implanted in a 47-year-old man who had sustained a recent massive myocardial infarction complicated by ventricular failure which remained unresponsive to intra-aortic balloon pump therapy and which was further complicated by irreversible ventricular fibrillation. Following implantation of the device and while awaiting a suitable donor organ for transplantation, further extension of the previous infarct resulted in left ventricular rupture and massive haemorrhage which led to his death. We report the successful use of the device in providing haemodynamic support, but caution against inordinate delay in bridging to transplantation patients who are at risk of extension of infarction.

Heart-Assist Devices↗
PubMed1990

Carcinoma of the colon and rectum in patients less than 20 years of age.

We report the cases of eight children and adolescents with adenocarcinoma of the colon treated at three large referral hospitals over a 25-year period. We recorded demographic factors, initial symptoms, stage at operation, type of operation, pathologic grade, and survival, and compared our results to those in the English literature. There were seven male patients and one female patient, with an average age of 15.1 years and an average duration of symptoms of 7 1/2 months. The most common initial complaint was rectal bleeding (6/8 patients, 75%). Pain, anemia, and abdominal distention were present in five of the eight patients (63%). Six of our eight patients (75%) had stage C or D disease at diagnosis, and six of the eight tumors (75%) were poorly differentiated. Only three of the eight patients lived for more than six months. Unexplained gastrointestinal bleeding or abdominal complaints in children should prompt a thorough investigation of the gastrointestinal tract.

Adenocarcinoma↗
PubMed1989

Formation of an intramolecular cystine disulfide during the reaction of 8-azidoguanosine 5'-triphosphate with cytosolic phosphoenolpyruvate carboxykinase (GTP) causes inactivation without photolabeling.

Phosphoenolpyruvate carboxykinase (GTP) (PEPCK) specifically utilizes a guanosine or inosine nucleotide as a substrate, yet it does not share extended sequence homology with other GTP-binding proteins, and the molecular basis for its nucleotide specificity is not understood. In an effort to locate the enzyme's nucleotide-binding site, we have studied the interaction of cytosolic PEPCK from rat liver with the photoprobe 8-azidoGTP, which fulfills the criteria of a specific photoaffinity label for PEPCK. The photoprobe binds reversibly to the enzyme prior to modification and at low concentrations causes greater than 60% inactivation (Ki = 1.2 microM). GTP provides nearly complete protection against inactivation by 8-azidoGTP, whereas phosphoenolpyruvate and metal ions provide partial protection. In addition, the photoprobe is a substrate for the enzyme and has a Km similar to that for GTP. However, the extent of covalent modification by [32P]8-azidoGTP as measured by three independent techniques is significantly lower than the extent of enzyme inactivation. Further investigation of this anomaly has revealed that the loss in enzymatic activity is caused by modification of a critical cysteine residue in a reaction that does not terminate with covalent attachment of the photolabel. Quantitation of the total free thiols of modified PEPCK shows that 2 mol of cysteine is lost per mole of inactivated enzyme. These results indicate that the photoinactivation of PEPCK by 8-azidoGTP is caused by the formation of an intramolecular cystine disulfide bridge, thus providing evidence for the existence of a pair of proximal cysteine residues within the GTP-binding site. The interaction of cysteine residues with the reactive photogenerated derivatives of 8-azidopurines is discussed.

Affinity Labels↗
PubMed1989

Artificial hearts.

Explore the source record for details and available documents.

Assisted Circulation↗
PubMed1989

Cysteine 288: an essential hyperreactive thiol of cytosolic phosphoenolpyruvate carboxykinase (GTP).

Phosphoenolpyruvate carboxykinase from the cytosol of rat liver has 13 cysteines, at least one of which is known to be very reactive and essential for catalytic activity (Carlson, G. M., Colombo, G., and Lardy, H. A. (1978) Biochemistry 17, 5329-5338). In order to identify the essential cysteine, this enzyme was modified with the fluorescent sulfhydryl reagent N-(7-dimethylamino-4-methyl-3-coumarinyl)maleimide. Incubation of phosphoenolpyruvate carboxykinase with a 10% molar excess of this maleimide at 0 degrees C results in the rapid and nearly complete loss of catalytic activity. Under these conditions, 1 mol of the maleimide is incorporated per mol inactivated enzyme. The substrate GDP provides almost complete protection against inactivation and modification, while phosphoenolpyruvate protects against the rate, but not the extent, of modification. The pH dependence of the rate of enzyme inactivation suggests that the modified residue has a pK alpha of approximately 7.0. Purification and sequencing of the labeled peptide identifies the hyperreactive essential cysteine as Cys-288. This cysteine lies between two putative phosphoryl-binding domains and within a hydrophobic sequence.

Amino Acid Sequence↗
PubMed1989

Cardiac surgical emergencies.

Cardiac surgical emergencies are broken down into three categories: cardiac trauma, aortic dissection, and surgery for acute myocardial infarctions. Emphasis is given to describing the presentation of patients with such problems, and to the salient aspects of the clinical strategies for managing each problem. An important goal of each section is focusing the critical care physician on the early recognition of cardiac surgical emergencies and providing him with some rationale for instituting an expeditious plan of therapy.

Aged↗
PubMed1985

Adverse effects of high dose aspirin on platelet adhesion to experimental autogenous vein grafts.

Prostacyclin (PGI2) production and platelet adhesion were studied in veins grafted into the arterial system of rabbits. Animal groups consisted of: no treatment; low dose aspirin (ASA) (0.5 mg . kg-1 X 24 h-1) plus dipyridamole (2 mg . kg-1 X 6 h-1); high dose ASA (40 mg . kg-1 X 24 h-1) plus dipyridamole (2 mg . kg-1 X 6 h-1); dipyridamole (2 mg . kg-1 X 6 h-1) alone. Results showed that vein grafts from animals treated with high dose ASA plus dipyridamole produced significantly less PGI2 than the other three groups (p less than 0.05 compared with the dipyridamole group; p less than 0.01 compared with the other two groups). In addition, there was significantly greater platelet deposition on the vein grafts from this high dose ASA group as compared to the low dose ASA group (p less than 0.05). By contrast, animals treated with dipyridamole alone had significantly less platelet deposition compared to both the control and high dose ASA groups (p less than 0.05). High dose ASA given to prevent thrombotic occlusion following coronary artery bypass grafting may, by reducing PGI2, result in enhanced platelet deposition. This in turn is likely to increase intimal hyperplasia as has been demonstrated previously with high dose ASA. Clinical studies, which have shown the early anti-thrombotic benefits of high dose ASA plus dipyridamole, have not measured graft intimal thickness. Since this process is an important cause of graft narrowing, ASA, in high dose, may adversely affect long-term graft survival.

6-Ketoprostaglandin F1 alpha↗
PubMed1985

Intrathecal morphine in cardiac surgery.

The effects of intrathecal morphine in 60 patients undergoing open-heart surgery were studied in an observer-blind control trial. The patients were randomly allocated into three groups of 20 each: (A) Control, (B) 2 mg and (C) 4 mg of intrathecal morphine. This study confirms that intrathecal morphine provides useful post-operative analgesia. Patients given intrathecal morphine required less postoperative analgesia and sedation and their respiratory function tests were less depressed than the control group. Since the completion of this study, reports have suggested that 1 mg of morphine intrathecally avoids the serious complications of respiratory depression. In the study described, the patients were electively ventilated post-operatively and respiratory depression was therefore not a problem. Of the other associated side-effects of intrathecal morphine, vomiting (20%) and pruritus (20%) proved the most troublesome.

Adolescent↗
PubMed1984

Activation of platelets by autogenous vein grafts is not prevented by acetylsalicylic acid and dipyridamole.

We have shown previously that experimental autogenous vein grafts activate platelets for up to four months following operation. In the present study, animals were treated with middle dose ASA (10 mg X kg-1 X 24 h-1) plus dipyridamole (8 mg X kg-1 X 24 h-1) and followed for 8 months. Despite this treatment, platelets were activated by the vein graft for up to four months after operation but not after this time. Similarly, treatment with low dose ASA (0.5 mg X kg-1 X 24 h-1) plus dipyridamole (8 mg X kg-1 X 25 h-1), high dose ASA (40 mg X kg-1 X 24 h-1) plus dipyridamole (8 mg X kg-1 X 24 h-1), or dipyridamole alone (8 mg X kg-1 X 24 h-1), did not prevent the vein graft-induced activation of platelets. Full inhibition of platelet arachidonic acid metabolism was demonstrated in the high dose ASA plus dipyridamole group. These results suggest that the interaction between the vessel wall and platelet is not inhibited by ASA plus dipyridamole. Platelets have first to be activated before causing intimal hyperplasia. Since aspirin and dipyridamole did not prevent activation of platelets by the graft, this drug combination is unlikely to prevent the development of intimal hyperplasia in the graft wall.

Adenosine Diphosphate↗
PubMed1984

Intimal thickening in autogenous vein grafts in rabbits: influence of aspirin and dipyridamole.

The effects of three different platelet modifying regimens on the degree of intimal thickening of autogenous vein grafts in rabbits were measured one month after operation. Dipyridamole alone (2 mg/kg/6 h) had little effect on the intimal thickness of these rabbits compared with that of controls (mean (1 SEM) for treated animals: 72.0 (7.9) micron; controls: 63.6 (6.0) micron). High dose acetylsalicylic acid (40 mg/kg/24 h) plus dipyridamole (2 mg/kg/6 h) increased intimal thickening significantly (85.8 (6.0) v 63.6 (6.2) micron; p = 0.05, n = 17). Low dose acetylsalicylic acid (0.5 mg/kg/24 h) plus dipyridamole (2 mg/kg/6 h) also increased intimal thickening (79.0 (6.1) v 63.6 (6.0] micron but not to a significant degree. It has previously been shown in vitro that acetylsalicylic acid increases the area of an exposed subendothelial arterial surface covered by platelets. Such an effect may explain our finding of increased intimal thickening with high dose acetylsalicylic acid plus dipyridamole.

Animals↗
PubMed1978

Influence of postoperative empyema on survival after pulmonary resection for bronchogenic carcinoma.

Fifty patients who had developed empyema after pulmonary resection for primary carcinoma of the lung were individually paired with patients who had not suffered this complication. Pairs were matched as far as possible for age, sex, extent of operation, histology of tumour, extent of primary spread, extent of lymphatic spread, and use of postoperative radiotherapy. Analysis of survival times both for the matched pairs and for the two groups of patients showed no significant difference in long-term survival. The results suggest that any immunological suppression of carcinoma cells due to sepsis in the pleural space is ineffective in prolonging survival.

Adult↗
PubMed1977

Milk bolus obstruction in the neonate.

Seventeen cases of neonatal intestinal obstruction due to inspissated milk curds were seen at this hospital in the 9 years 1964-1972. The obstruction started on the 2nd to 10th day of life. Half the babies passed blood from the rectum and in most the x-rays were diagnostic. All survived, 14 after operation and 3 after medical treatment with a Gastrografin enema. Incomplete absorption of solids, particularly the fat from cows' milk feeds, is suggested as the cause.

Animals↗