Biomedical subjects

C R MacKenzie

Publications and source records attributed to C R MacKenzie.

At least 19 recordsLinked to original sources

PubMed1992

Supervised fitness walking in patients with osteoarthritis of the knee. A randomized, controlled trial.

OBJECTIVE: To assess the effect of a program of supervised fitness walking and patient education on functional status, pain, and use of medication in patients with osteoarthritis of the knee. DESIGN: An 8-week randomized, controlled trial. SETTING: Inpatient and outpatient services of an orthopedic hospital in an academic medical center. PATIENTS: A total of 102 patients with a documented diagnosis of primary osteoarthritis of one or both knees participated in the study. Data were obtained on 47 of 51 intervention patients and 45 of 51 control patients. INTERVENTIONS: An 8-week program of supervised fitness walking and patient education or standard routine medical care. MEASUREMENTS: Patients were evaluated and outcomes assessed before and after the intervention using a 6-minute test of walking distance and scores on the physical activity, arthritis impact, pain, and medication subscales of the Arthritis Impact Measurement Scale (AIMS). RESULTS: Patients randomly assigned to the walking program had a 70-meter increase in walking distance relative to their baseline assessment, which represents an improvement of 18.4% (95% Cl, 9.8% to 27.0%). In contrast, controls showed a 17-meter decrease in walking distance relative to their baseline assessment (P less than 0.001). Improvements in functional status as measured by the AIMS physical activity subscale were also observed in the walking group but not in the control group (P less than 0.001); patients assigned to the walking program improved 39% (Cl, 15.6% to 60.4%). Although changes in scores on the arthritis impact subscale were similar in the two groups (P = 0.093), the walking group experienced a decrease in arthritis pain of 27% (Cl, 9.6% to 41.4%) (P = 0.003). Medication use was less frequent in the walking group than in the control group at the post-test (P = 0.08). CONCLUSIONS: A program of supervised fitness walking and patient education can improve functional status without worsening pain or exacerbating arthritis-related symptoms in patients with osteoarthritis of the knee.

Adult↗

PubMed1992

Laryngeal involvement in systemic lupus erythematosus.

Laryngeal involvement in systemic lupus erythematosus (SLE) can range from mild ulcerations, vocal cord paralysis, and edema to necrotizing vasculitis with airway obstruction. In this report, four cases showing the range of severity of this disease manifestation are presented, accompanied by a comprehensive review of the literature. The clinical course of 97 patients with laryngeal involvement with SLE are reviewed, of whom 28% had laryngeal edema and 11% had vocal cord paralysis. In the majority of cases, symptoms such as hoarseness, dyspnea, and vocal cord paralysis resolved with corticosteroid therapy. Other, less common causes of this entity included subglottic stenosis, rheumatoid nodules, inflammatory mass lesions, necrotizing vasculitis, and epiglottitis. The clinical presentation of laryngeal involvement in patients with SLE follows a highly variable course, ranging from an asymptomatic state to severe, life-threatening upper airway compromise. With its unpredictable course and multiple causations, this complication remains a diagnostic and therapeutic challenge to physicians involved in the care of patients with SLE.

Adult↗

PubMed1992

Predicting postoperative pulmonary complications. Is it a real problem?

To identify predictors of postoperative pulmonary complications, a population of 278 patients, mainly hypertensive and diabetic patients undergoing elective general surgery was studied; 60% of the patients underwent abdominal surgery. Of the 278 patients, 6% had postoperative pulmonary complications: 3% had radiographic evidence of infiltrates or segmental atelectasis and 3% had clinical evidence of atelectasis. Among the two thirds of patients undergoing abdominal surgery, only patients with underlying asthma or chronic bronchitis were at increased risk. Generally, patients with better exercise tolerance by self-report, walking distance, or cardiovascular classification had lower rates. Pulmonary function tests did not help to delineate patients at higher risk of postoperative pulmonary complications. Simple clinical information provided as much data about the patients' risk as pulmonary function tests. Many of these complications occurred in patients who sustained other types of postoperative morbidity, suggesting that predicting and preventing postoperative cardiac morbidity may be the best approach to reducing postoperative pulmonary morbidity.

Aged↗

PubMed1991

Bacterial expression and secretion of various single-chain Fv genes encoding proteins specific for a Salmonella serotype B O-antigen.

Active single-chain Fv molecules encoded by synthetic genes have been expressed and secreted to the periplasm of Escherichia coli using the ompA secretory signal. Four different constructs were developed to investigate the effects of peptide linker design and VL-VH orientation on expression, secretion, and binding to a Salmonella O-polysaccharide antigen. Peptide linker sequences derived from the elbow regions of the Fab molecule were used alone or in combination with the flexible (GGGGS)2 sequence. VL and VH domain order in the single chain molecules had a profound effect on the level of secretion but hardly influenced total expression levels, which were approximately 50 mg/liter, chiefly in the form of inclusion bodies. With VL in the NH2-terminal position, the amount of secreted product obtained was 2.4 mg/liter, but when VH occupied this position the yield was less than 5% of this value. Enzyme immunoassays of the four products showed domain order and linker sequence affected antigen binding by less than an order of magnitude. Attempts to express active Fv from dicistronic DNA were unsuccessful, but active Fv was obtained from single-chain Fv by enzymic cleavage at a site in the elbow linker peptide. The thermodynamic binding parameters of intact and cleaved single-chain Fvs determined by titration microcalorimetry were similar to those of bacterially produced Fab and mouse IgG.

Amino Acid Sequence↗

PubMed1991

Synthesis and expression in Escherichia coli of cistronic DNA encoding an antibody fragment specific for a Salmonella serotype B O-antigen.

A 1460-bp DNA encoding the two chains of the antigen-binding fragment (Fab) portion of a monoclonal antibody have been chemically synthesized and expressed in Escherichia coli. The antibody, Se155-4, is specific for a Salmonella serogroup B O-antigen and its crystal structure is under investigation. The genes were synthesized according to a strategy that allows for easy manipulation in genetic engineering studies of the Fab-binding site. Each gene is preceded by the ompA secretory signal and a ribosome-binding site, and has been expressed from the two-cistron DNA under the control of the lac promoter. Active Fab of 50 kDa with an inter-chain disulfide bond has been isolated from the periplasm of E. coli in a one-step affinity purification in high yield (2 micrograms/ml of cells). The bacterially produced Fab is as active as purified mouse Fab in antigen-binding and competitive immunoassays. This is the first example of a completely synthetic Fab gene and provides an ideal system to probe the nature of antigen binding by anti-carbohydrate antibodies.

Amino Acid Sequence↗

PubMed1991

Relating patient characteristics at the time of admission to outcomes of hospitalization.

In clinical practice, physicians informally address patient characteristics such as illness severity, comorbidity, functional status and stability when considering prognosis and diagnostic or therapeutic interventions. These same attributes, more formally measured, have been used as measures of casemix in clinical research to classify patients into similar risk strata. To determine whether physician estimates of illness severity, function status and stability were predictive of morbidity, mortality, length of stay and average daily ancillary charges, a cohort of 604 patients was studied. The predictive ability of the patient characteristics were found to be outcome specific. Illness severity was a significant predictor of in-hospital morbidity and mortality, length of stay and charges (p less than 0.001). Functional status was predictive of in-hospital morbidity and mortality, 1 year mortality, length of stay and charges (p less than 0.01). Physician estimates of stability were predictive only of morbidity (p less than 0.01) and comorbidity was only a preditor of 1 year mortality (p less than 0.001). Stratifying patients on the basis of specific clinical characteristics determined at the time of admission will be useful in studies of patient outcomes and resource utilization.

Aged↗

PubMed1991

Scanning of key residues in antibody binding sites by two saturation-mutagenesis approaches.

The complementarity-determining region 3 of the heavy chain (CDRH3) generally contributes the most to antibody-antigen binding. His101H in CDRH3 of the antibody Se155-4, which is specific for a trisaccharide epitope of Salmonella serotype B O-antigen, was mutated systematically into all nineteen other amino acids by a double mutation approach. Enzyme immunoassay (EIA) and affinity chromatography showed that the Asn, Gln, Gly and Ser mutants exhibited moderate to strong activity. Some mutants, such as Thr and Pro, had weak binding activity, while the acidic and hydrophobic amino acid substitutions resulted in complete loss of activity. A second mutation approach which randomly changed a selected residue into all other nineteen amino acids, while precluding wild-type transformants, is also described.

Amino Acid Sequence↗

PubMed1991

Risk for postoperative congestive heart failure.

To identify predictors of postoperative congestive heart failure (CHF), a high-risk population, mainly hypertensive and diabetic patients undergoing elective general operations, was studied. Of the 254 patients, 6 per cent had postoperative CHF. Among patients with preoperative cardiac disease (that is, previous myocardial infarction, valvular disease or CHF), 17 per cent had postoperative CHF; in contrast with less than 1 per cent of those without cardiac disease (p less than 0.001). Patients with diabetes were also at high risk (12 versus 2 per cent, p less than 0.005), particularly those with cardiac disease. Patients who had equal to or greater than 40 millimeters of mercury increases or decreases intraoperatively in mean arterial pressure in relation to preoperative baseline had increased postoperative failure rates (p less than 0.02). Of note, postoperative failure rates were highest among patients with less than 500 milliliters per hour of net intake (input and output) (p less than 0.03). Risk for postoperative CHF was restricted to patients with preoperative symptomatic cardiac disease and was especially high if patients also had diabetes. Intraoperative fluctuations in mean arterial pressure increased the probability of postoperative failure, while the intraoperative administration of higher net volumes of fluid was associated with decreased risk.

Aged↗

PubMed1990

Synthesis and expression in Escherichia coli of DNA encoding the murine lambda 1 chain of a monoclonal antibody specific for Salmonella serotype B O-antigen.

A 658 bp DNA sequence corresponding to the murine lambda 1 chain of a monoclonal antibody, Se155-4, specific for the Salmonella serotype B O-antigen, was designed using Escherichia coli preferred codons and chemically synthesized by ligation of synthetic fragments into a linearized plasmid followed by transformation into E. coli. A synthetic signal peptide (ompA) was fused to express the L chain as a free polypeptide into the periplasm of E. coli cells. After isolation and purification, heterologous recombination of the E. coli L chain with mouse H chain gave an active antigen-binding protein. The activity was 15-20% when compared to protein created by an equivalent association of isolated natural mouse L and H chains as measured by a direct EIA assay. In inhibition experiments with the polysaccharide antigen, the two proteins showed identical titration curves and 50% inhibition points, indicating comparable KA values.

Amino Acid Sequence↗

PubMed1990

Preoperative characteristics predicting intraoperative hypotension and hypertension among hypertensives and diabetics undergoing noncardiac surgery.

We prospectively studied patients with hypertension and diabetes undergoing elective noncardiac surgery with general anesthesia to test the hypothesis that patients at high risk for prognostically significant intraoperative hemodynamic instability could be identified by their preoperative characteristics. Specifically we hypothesized that patients with a low functional capacity, decreased plasma volume, or significant cardiac comorbidity would be at high risk for intraoperative hypotension and those with a history of severe hypertension would be at risk for intraoperative hypertension. Patients who had a preoperative mean arterial pressure (MAP) greater than or equal to 110, a walking distance of less than 400 m, or a plasma volume less than 3000 cc were at increased risk of intraoperative hypotension (i.e., more than 1 hour of greater than or equal to 20 mmHg decreases in the MAP). Hypotension was also more common among patients having intra-abdominal or vascular surgery, and among those who had operations longer than 2 hours. Patients older than 70 years or with a decreased plasma volume were at increased risk of having more than 15 minutes of intraoperative elevations of greater than or equal to 20 mmHg over the preoperative MAP in combination with intraoperative hypotension; this was also more common when surgery lasted more than 2 hours. Patients who had intraoperative hypotension tended to have an immediate decrease in MAP at the onset of anesthesia and were often purposefully maintained at MAPs less than their usual level during surgery with fentanyl and neuromuscular blocking agents. Patients who had intraoperative hyper/hypotension tended to have repeated elevations in MAP above their preoperative levels during the course of surgery, and such elevations precipitated interventions with neuromuscular blocking agents and/or fentanyl. Neither pattern was more common among patients who developed net intraoperative negative fluid balances. Both hypotension and hyper/hypotension were associated with increased renal and cardiac complications after operation. Patients with cardiac disease, especially diabetics, and those with negative fluid balances also had increased complications. Preoperative characteristics influence the susceptibility to intraoperative hypotension and hypertension, which are related to postoperative complications.

Aged↗

PubMed1990

Intraoperative blood pressure. What patterns identify patients at risk for postoperative complications?

While monitoring blood pressure is a routine part of intraoperative management, several methods have been proposed to characterize intraoperative hemodynamic patterns as predictors of postoperative complications. In this prospective study of a high-risk population of hypertensive and diabetic patients undergoing elective noncardiac surgery, one objective was to compare different approaches to the assessment of intraoperative hemodynamic patterns to identify those patterns most likely to be associated with postoperative complications. Twenty-one per cent of the 254 patients sustained cardiac or renal complications after operation. Patients with more than 1 hour of greater than or equal to 20-mmHg decreases in mean arterial pressure (MAP) or patients with less than 1 hour of greater than or equal to 20-mmHg decreases and more than 15 minutes of greater than or equal to 20-mmHg increases were at highest risk for postoperative complications. Together these two patterns had a 46% sensitivity rate and a 70% specificity rate in predicting postoperative complications. Using 20% change in intraoperative MAP produced results nearly identical to 20-mmHg changes. When the duration of 20-mmHg changes was accounted for, changes of a greater magnitude (e.g., 40 mmHg) were not significant independent predictors of complications. The use of the mean difference from preoperative MAP was misleading because patients who experienced both high and low MAPs tended to have nearly normal mean MAPs, but high complication rates. The absolute magnitude of intraoperative MAPs, regardless of the preoperative levels, also was evaluated. The overall mean intraoperative MAP was not a significant predictor of complications. Specific intraoperative MAPs (e.g., less than 70 mmHg and more than 120 mmHg) also were evaluated. While neither was a significant predictor, there was a trend for increased complications among patients whose MAPs decreased to less than 70 mmHg. Intraoperative blood pressure should be analyzed in relation to the patient's preoperative blood pressure. Prolonged changes of more than 20 mmHg or 20% in relation to preoperative levels were significantly related to complications.

Blood Pressure↗

PubMed1990

Purification and properties of an acetylxylan esterase from Fibrobacter succinogenes S85.

An acetylxylan esterase (EC 3.1.1.6) was purified to apparent homogeneity from the nonsedimentable extracellular culture fluid of Fibrobacter succinogenes S85 grown on cellulose. This enzyme had an apparent molecular mass of 55 kDa and an isoelectric point of 4.0. The temperature and pH optima were 45 degrees C and 7.0, respectively. The apparent Km and Vmax were 2.7 mM and 9,100 U/mg, respectively, for the hydrolysis of alpha-naphthyl acetate. The enzyme cleaved acetyl residues from birchwood acetylxylan but did not hydrolyze carboxymethylcellulose, larchwood xylan, ferulic acid-arabinose-xylose polymer, p-nitrophenyl-alpha-L-arab-inofuranoside, or longer-chain naphthyl fatty acid esters. The esterase enzyme may play a role in enhancing hemicellulose degradation by F. succinogenes, thereby allowing it greater access to cellulose present in forage cell walls.

Animals↗

PubMed1989

Identification of three distinct Clostridium thermocellum xylanase genes by molecular cloning.

Three genes coding for xylanase synthesis in Clostridium thermocellum were cloned and expressed in Escherichia coli. Genomic DNA from Clostridium thermocellum was digested to completion with HindIII, BamHI, and SalI. The fragments were ligated into the corresponding sites of pUC19 and transformed into Escherichia coli. Two of the genes encoded for xylanases which depolymerized xylans but were unable to extensively convert these substrates to reducing sugar. The third gene encoded for an enzyme that extensively hydrolyzed xylan. The insert containing the latter gene was subjected to extensive mapping and was found to encode for a xylanase with a molecular weight of approximately 25,000. The protein product of the cloned gene was obtained in a relatively pure form by heat treatment, ion exchange and gel permeation steps. The enzyme was quite stable to high temperatures with a half-life of 24 h at 70 degrees C.

Cloning, Molecular↗

PubMed1989

The post-operative electrocardiogram and creatine kinase: implications for diagnosis of myocardial infarction after non-cardiac surgery.

The objective of this study was to evaluate different approaches to the diagnosis of post-operative myocardial infarction. A total of 232 patients, mostly hypertensive and/or diabetic patients, who were undergoing elective non-cardiac surgery were evaluated pre-operatively. They were followed serially from the day of operation to discharge or the sixth post-operative day with daily clinical evaluations, electrocardiograms, creatine kinase and creatine kinase isoenzymes. In total 22% (51/232) of the patients had post-operative ECG changes in two or more leads. Only 1% developed new Q waves; most of the changes involved changes in the T or ST segments. Seventy percent of patients who had changes in their electrocardiogram were completely asymptomatic. The highest risk of ECG changes or symptoms occurred on the day of operation and the first post-operative day; evidence of post-operative infarction was infrequent after the second post-operative day. Creatine kinase levels rose an average of 250-300 IU on the first and second post-operative day (also the peak time for post-operative ECG changes), reducing its utility as an adjunct to the diagnosis of post-operative infarctions. Importantly, 52% (12/23) of the patients who had greater than or equal to 5% MB isoenzyme had neither ECG changes nor symptoms; the diagnosis of a myocardial infarction should not be made in these patients. In summary, most patients who experience ischemia or infarction post-operatively are asymptomatic. Symptoms should not be required for the diagnosis of post-operative infarction. Seemingly minor differences in criteria can produce major discrepancies in post-operative myocardial infarction rates (from 1 to 9%). The development of a final set of criteria will require further study but the diagnosis of post-operative infarction should probably be based on ECG changes, their duration and consistency, and the association of a positive MB fraction.

Aged↗

PubMed1989

Postoperative changes in serum creatinine. When do they occur and how much is important?

The objective of this study was to evaluate the use of the serum creatinine in following postoperative renal function. In this prospective study of 278 patients (mainly hypertensives and diabetics) undergoing noncardiac surgery, the serum creatinines were followed from the first through the sixth postoperative day. Creatinine clearances were evaluated before operation and on the fourth to fifth postoperative day. During the first six days after the operation, 23% (65 of 278 patients) had an increase of serum creatinine greater than or equal to 20%. Such increases were sustained for greater than or equal to 48 hours in 12% of the patients (32 of 278), and half of these patients had not returned to their initial level of renal function by the time of discharge. Patients who sustained such a deterioration were at risk for nonoliguric renal failure if they had a subsequent insult (i.e., hypotension, reoperation, angiography, aminoglycosides). Such increases occurred early in the postoperative period--on the first or second postoperative day. As judged by the creatinine clearances, postoperative increases of greater than or equal to 20% in the serum creatinine identified most patients whose clearance fell more than 50%, although the serum creatinine did not accurately reflect changes in creatinine clearance among those patients who had undergone an amputation. It is concluded that the serum creatinine is useful in monitoring postoperative renal function. Of those patients who had postoperative increases in serum creatinine sustained for greater than or equal to 48 hours, as many as one third had evidence of impairment in renal function at the time of discharge.

Acute Kidney Injury↗

PubMed1989

The preoperative and intraoperative hemodynamic predictors of postoperative myocardial infarction or ischemia in patients undergoing noncardiac surgery.

Among hypertensive and diabetic patients undergoing elective noncardiac surgery, preoperative status and intraoperative changes in mean arterial pressure (MAP) were evaluated as predictors of postoperative ischemic complications. Of 254 patients evaluated before operation and monitored during operation, 30 (12%) had postoperative cardiac death, ischemia, or infarction. Twenty-four per cent of patients with a previous myocardial infarction or cardiomegaly had an ischemic postoperative cardiac complication. Only 7% of those without either of these conditions sustained an ischemic complication. No other preoperative characteristics, including the presence of angina, predicted ischemic cardiac risk. Nineteen per cent of patients who had 20 mm Hg or more intraoperative decreases in MAP lasting 60 minutes or more had ischemic cardiac complications. Patients who had more than 20 mm Hg decreases in MAP lasting 5 to 59 minutes and more than 20 mm Hg increases lasting 15 minutes or more also had increased complications (p less than 0.03). Changes in pulse were not independent predictors of complications and the use of the rate-pressure product did not improve prediction based on MAP alone. In conclusion patients with a previous infarction or radiographic cardiomegaly are at high risk for postoperative ischemic complications. Prolonged intraoperative increases or decreases of 20 mm or more in MAP also resulted in a significant increase in these potentially life-threatening surgical complications.

Adult↗

PubMed1989

Identification of two distinct Bacillus circulans xylanases by molecular cloning of the genes and expression in Escherichia coli.

Two genes coding for xylanase synthesis in Bacillus circulans were cloned and expressed in Escherichia coli. After digestion of genomic DNA from Bacillus circulans with EcoRI and PstI, the fragments were ligated into the corresponding sites of pUC19 and transformed into Escherichia coli. Restriction enzyme mapping of the two inserts coding for xylanase activity indicated distinctly different nucleotide sequences. Cross-hybridization assays confirmed the absence of sequence homology between the two genes. In vitro transcription-translation assays indicated that the cloned genes encoded for proteins with molecular weights of 22,000 and 59,000. The gene products displayed different substrate specificities. The 22,000-dalton enzyme readily hybrolyzed aspeen, larchwood, and oat spelt xylans, whereas the second was unable to extensively depolymerize oat spelt xylan and resulted in very limited reducing sugar release from any of the xylan substrates tested. Both of the xylanases had isoelectric points of approximately 9.0.

Bacillus↗

PubMed1989

Hyperexpression of a Bacillus circulans xylanase gene in Escherichia coli and characterization of the gene product.

A 4.0-kilobase (kb) fragment of Bacillus circulans genomic DNA inserted into pUC19 and encoding endoxylanase activity was subjected to a series of subclonings. A 1.0-kb HindIII-HincII subfragment was found to code for xylanase activity. Maximum expression levels were observed with a subclone that contained an additional 0.3-kb sequence upstream from the coding region. Enhancer sequences in the upstream region are thought to be responsible for these high expression levels. Southern hybridization analyses revealed that the cloned gene hybridized with genomic DNA from Bacillus subtilis and Bacillus polymyxa. Xylanase activity expressed by Escherichia coli harboring the cloned gene was located primarily in the intracellular fraction. Levels of up to 7 U/ml or 35 mg/liter were obtained. The protein product was purified by ion exchange and gel permeation chromatography. The xylanase had a molecular weight of 20,500 and an isoelectric point of 9.0.

Bacillus↗