PubMed Health⌕ Search

Biomedical subjects

S Carson

Publications and source records attributed to S Carson.

At least 19 recordsLinked to original sources
PubMed1992

Alternative techniques of cardioplegia.

BACKGROUND: Although normothermic cardioplegia has been used with acceptable clinical results, no studies have previously been performed to determine the metabolic consequences of these various techniques of myocardial protection. Therefore, we have performed a randomized clinical trial to assess the effects of three cardioplegic techniques on myocardial metabolic recovery. METHODS AND RESULTS: Seventy-four patients undergoing coronary artery bypass graft surgery were randomized to receive normothermic antegrade blood cardioplegia (n = 25), normothermic retrograde blood cardioplegia (n = 23), or intermittent cold antegrade blood cardioplegia (n = 26). Myocardial oxygen consumption and lactate production, adenine nucleotides, and adenine nucleotide degradation products were measured during the operation, and cardiac creatine kinase isoenzyme (CK-MB) release was assessed after surgery. Warm antegrade cardioplegia maximized myocardial oxygen consumption during cardioplegic delivery. Postoperative CK-MB release was less after warm antegrade cardioplegia, but the difference was not statistically significant. Warm retrograde cardioplegia resulted in the greatest degree of anaerobic lactate production but did not increase morbidity and mortality. Perioperative myocardial infarctions and postoperative low-output syndrome were most common after cold cardioplegia, but this trend was not statistically significant. During warm antegrade cardioplegia, adenosine triphosphate (ATP) was metabolized to diffusible precursors, which were washed out during cardioplegic infusion. Warm retrograde cardioplegia produced a breakdown of ATP to inosine and hypoxanthine, small molecules that accumulated during the cross-clamp period and were not washed out, perhaps because of inadequate perfusion with retrograde delivery. During cold cardioplegia, ATP was dephosphorylated, and adenosine diphosphate, adenosine monophosphate, and adenosine accumulated. These compounds were not regenerated to ATP but were not washed out of myocytes because they are large anionic molecules. CONCLUSIONS: Intermittent cold cardioplegia inhibited mitochondrial function but prevented the degradation of adenine nucleotides. Warm antegrade cardioplegia had the greatest myocardial oxygen consumption, and warm retrograde cardioplegia had the greatest anaerobic lactate production. There were no differences in clinical outcomes between cardioplegic groups.

Adenosine Triphosphate↗
PubMed1992

The effect of warm heart surgery on postoperative bleeding.

The effects of normothermic systemic perfusion (35 degrees to 37 degrees C; n = 73) were compared with those of moderately hypothermic systemic perfusion (25 degrees to 29 degrees C; n = 73) with respect to blood loss, transfusion requirements, and platelet levels in 146 patients undergoing isolated, primary coronary artery bypass grafting. In addition, most patients were given an antifibrinolytic medication during operation as follows: tranexamic acid (10 gm intravenously; n = 63), epsilon-aminocaproic acid (15 gm intravenously; n = 63), or no drug as a control. (n = 20). Normothermic patients tended to bleed less at 24 hours (warm, 864 +/- 42 ml and cold, 918 +/- 68 ml), but these differences were not statistically significant. Patients receiving either tranexamic acid or epsilon-aminocaproic acid, regardless of perfusion temperature, bled less after 6, 12, and 24 hours than did cold control patients (p less than 0.05). Warm control patients also bled less than did cold control patients after 6 or 12 hours (p less than 0.05), and neither drug further reduced blood loss in these patients. Circulating platelet levels were better preserved in patients receiving either tranexamic acid or epsilon-aminocaproic acid and in patients with warm perfusion and no drug than in cold control patients. Normothermic systemic perfusion, tranexamic acid, and epsilon-aminocaproic acid each reduced postoperative blood loss and preserved platelets.

Aminocaproic Acid↗
PubMed1991

DNase I hypersensitive sites flank the mouse class II major histocompatibility complex during B cell development.

The mouse class II major histocompatibility complex (MHC) encodes a polymorphic, multigene family important in the immune response, and is expressed mainly on mature B cells, on certain types of dendritic cells and is also inducible by gamma-interferon on antigen presenting cells. To study the regulatory elements which control this expression pattern, we have examined the chromatin structure flanking the class II MHC region, in particular during B cell differentiation. Using a panel of well-characterised mouse cell lines specific for different stages of B cell development (pre-B, B, plasma cell) as well as non-B cell lines, we have mapped the DNase I hypersensitive (DHS) sites adjacent to the mouse MHC class II region. The results presented show, for the first time that there are specific hypersensitive sites flanking the class II MHC locus during pre B cell, B cell and plasma cell stages of B cell differentiation, irrespective of the status of class II MHC expression. These hypersensitive sites are not found in T cell, fibroblast or uninduced myelomonocytic cell lines. This suggests that these DHS sites define a developmentally stable, chromatin structure, which can be used as a marker of B cell lineage commitment and may indicate that a combination of these hypersensitive sites reflect regulatory proteins involved in the immediate expression of a particular class II MHC gene or possibly control of the entire locus.

Animals↗
PubMed1991

Optimal delivery of blood cardioplegia.

A prospective randomized controlled trial was performed to determine optimal flow rates and hemoglobin concentrations for continuous normothermic blood cardioplegia and to compare warm heart surgery with standard intermittent cold blood cardioplegia. Thirty-five patients received intermittent cold blood cardioplegia, low hemoglobin low flow, low hemoglobin high flow, high hemoglobin low flow, or high hemoglobin high flow warm blood cardioplegia (seven patients per group: low hemoglobin, 50 g/l; high hemoglobin, 80 g/l; low flow, less than 80 ml/min; high flow, greater than 80 ml/min). Hypothermia resulted in a significantly greater accumulation of ADP and AMP during cross clamp, consistent with impaired mitochondrial function. Low hemoglobin low flow warm blood cardioplegia increased myocardial oxygen consumption and coronary sinus blood flow after cross clamp release, and also decreased lactate consumption. Postoperative myocardial performance and diastolic compliance were reduced in low hemoglobin low flow warm patients, and diastolic compliance was increased with high hemoglobin high flow warm blood cardioplegia when compared with cold patients. In this study, continuous normothermic cardioplegia was safe when delivered at 80 ml/min or greater, with a hemoglobin concentration of at least 80 g/l, affording myocardial metabolic and functional recovery comparable to that found after intermittent cold blood cardioplegia.

Blood↗
PubMed1979

Biocompatibility evaluation of casting alloys in hamsters.

A number of base metal and low gold-content alloys were evaluated in hamster cheek pouches for biocompatibility. No adverse weight changes and no abnormal behavioral patterns were noted in any of the test groups over the 14-day period of the study. Gross examination of the cheek pouches containing the alloys was no different from that of the controls. None of the alloys tested showed significant adverse histopathologic reactions. The recorded changes in incidences and degree of response were essentially no different from those of the negative control material.

Animals↗
PubMed1978

Colonic varices. A complication of pancreatitis with splenic vein thrombosis.

A patient with recurrent gastrointestinal bleeding was found to have varices at the splenic flexure at colonoscopy. Angiography revealed complete occlusion of the splenic vein. Although the patient did not have cirrhosis, he did have a history of pancreatitis which presumably was responsible for the splenic vein thrombosis. This case represents a compartmentalized form of portal hypertension which requires careful endoscopic and radiographic studies for proper evaluation. Successful treatment was accomplished by splenectomy.

Colon↗
PubMed1978

Immune response in urinary tract infection determined by radioimmunoassay and immunofluorescence: serum antibody levels against infecting bacterium and Enterobacteriaceae common antigen.

A solid-phase radioimmunoassay (RIA) procedure was compared with the indirect fluorescent antibody (IFA) test in a serological study of 76 female adults with urinary tract infections. Relative serum antibody activity was determined against patients' homologous infecting enterobacteria by RIA and IFA and against heterologous enterobacterial common antigen (Escherichia coli O14) by RIA. There was marked correlation between results of the IFA and RIA methods using the homologous system; 22 of 51 patients (43%) with pyelonephritis had significantly elevated serum antibody activity by both IFA (titers greater than or equal to 512) and RIA (binding ratio greater than or equal to 2.0) when compared with normal serum controls; three had significant antibody activity detectable by RIA only. Eighteen (72%) of 25 patients with pyelonephritis had RIA binding ratios of greater than or equal to 2.0 against their homologous bacterial isolates and the enterobacterial common antigen; an additional 6 patients had binding ratios of greater than or equal to 2.0 against the antigen only. All 25 patients with cystitis had low serum antibody levels by IFA and RIA when tested against their own isolate as well as enterobacterial common antigen. The RIA procedure was objective, quantitative, and less tedious to perform than IFA.

Adult↗
PubMed1978

Cytomegalovirus retinitis: two cases occurring after renal transplantation.

Cytomegalovirus (CMV) retinitis is reported in 2 patients who received immunosuppressive medication after cadaveric renal transplantation. The clinical features of this disease as well as the differential diagnosis are presented. Reduction in the amount of immunosuppressive drugs given postoperatively is suggested as the definitive treatment of this disease. Available specific antiviral chemotherapeutic agents were ineffective against CMV retinitis. This finding may be modified at a later date, with the introduction and use of new effective and safe antiviral drugs.

Adult↗
PubMed1977

Lipoperoxidation in human and rat brain tissue: developmental and regional studies.

Lipoperoxidation in human and rat brain was studied on the basis of formation in vitro of thiobarbituric acid positive (TBA) materials. In rats aged 1--540 days, the endogenous pools of reactive material were unchanged but on subsequent incubation of their homogenates the level of TBA-positive materials fell by 3 fold (fresh weight basis) and 5.4 fold (protein basis). In human brain, there was a distinct regional distribution of reactive materials in the endogenous pools with highest levels in the cerebellar vermis, and lower levels in thalamus, cortical regions, substantia nigra, caudate nucleus, pallidum, putamen, and hypothalamus. Only trace levels were detected in the pineal gland. On incubation all values rose 13--25 fold within 3 h at 37 degrees C except for cerebellar vermis which was increased 6 fold, and pineal gland 9 fold. Four TBA-positive materials were separated from rat brain by TLC, three of which were identical to malonyldialdehyde and its polymers. Lipoperoxidation in rat homogenates was inhibited 75--90% by sera from several different sources. The inhibitory properties were unaffected by dialysis and were not reproduced by addition of a large number of low and high mol. wt. components including vitamin E when added in concentrations equal to or exceeding that of native serum.

Adult↗
PubMed1977

Cytomegalovirus retinitis secondary to chronic viremia in phagocytic leukocytes.

We studied the relationship between the duration and intensity of cytomegalovirus viremia, cytomegalovirus complement fixing antibody, and cytomegalovirus retinitis in 61 renal transplant recipients. Five (8%) patients had chronic viremia which lasted more than six months. Two of the five developed typical cytomegalovirus retinitis and a severe fungal infection after intensive viremia of more than 11 months' duration. Retinitis did not develop in 22 patients with short-term viremia. Infectious cytomegalovirus was largely associated with polymorphonuclear leukocytes, but the virus was associated with monocytes during the immature granulocytic response accompanying one patient's terminal illness.

Adult↗
PubMed1977

Electrolyte and acid-base disturbances in the management of leukemia.

Electrolyte disturbances in leukemia can be the result of the disease process or drug therapy. One group of electrolyte abnormalities is related to the stage of the leukemic process. Included in this group are newly diagnosed patients who may show elevated serum potassium, phosphorus, and magnesium--a result of their release from malignant cells after cytotoxic therapy or their accumulation due to urate nephropathy. Patients in remission usually have normal serum electrolyte concentrations, but acute leukemia patients during relapse may have hypokalemia, hypophosphatemia, and hypomagnesemia. This imbalance may be related to cellular uptake of these electrolytes in the presence of inadequate dietary intake. Other factors contributing to electrolyte derangements, and related to the leukemic process, include hyponatremia and hypochloremia secondary to the SIADH, hypokalemia in acute monocytic or acute myelomonocytic leukemia due to lysozyme-induced tubular damage, hypercalcemia possibly secondary to leukemic infiltration of bone or parathyroid glands (with PTH release), or production of a PTH-like substance by leukemic cells. Nonspecific factors related to the disease process which may aggravate the electrolyte imbalance include gastrointestinal loss through nausea, vomiting, and malnutrition. The drug-related electrolyte abnormalities include cyclophosphamide- and vincristine-induced SIADH; decreased serum sodium, chloride, potassium, and calcium concentrations as a result of polymyxin B nephrotoxicity; hypokalemia and hypomagnesemia secondary to amphotericin B; hypocalcemia, hypophosphatemia, and hyperphosphaturia due to L-asparaginase-induced hypoparathyroidism; hypokalemia due to a nonreabsorbable anion effect of antibiotics in the distal tubule or changes in membrane ionic transport of all cells by large doses of antibiotics. Electrolyte disturbance in leukemia thus have a multifactorial pathogenesis which can best be delineated according to the stage of the leukemic process and the drugs being used. Recognition of the cause or causes in a particular patient is essential for an effective approach to management. This review emphasizes the need for routine measurement of serum electrolytes during all phases of the leukemic process.

Acid-Base Imbalance↗
PubMed1977

Biochemical studies on muscarinic receptors.

Muscarinic receptors have been characterized in smooth muscle and brain by the binding of reversible (e.g. atropine, quinuclidinylbenzylate) or irreversible (benzilylcholine or propylbenzilylcholine mustards) ligands. There is a close correlation between affinity constants derived from binding experiments and the affinities of muscarinic ligands for these sites obtained in pharmacological experiments on smooth muscle. Whereas atropine shows a single high affinity binding component (in subcellular preparations) several other ligands (QNB, ACh, oxotremorine) show multiple affinity binding. This indicated the existence of several types of binding sides which show selectivity toward certain cholinergic effectors. Most detergents inhibit the binding of ligands to the receptor site and therefore cannot be used to solubilize the receptor protein from the membrane. Treatment of brain subcellular membrane preparations with high salt concentrations (2M NaI) solubilize proteins which possess the muscarinic ligand binding properties observed in the membrane preparation. The affinities for muscarinic antagonists however are decreased, which suggests that a conformational change occurs in the protein upon solubilization.

Acetylcholine↗