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Biomedical subjects

K M McIntyre

Publications and source records attributed to K M McIntyre.

At least 19 recordsLinked to original sources
PubMed1997

Prolonged weightlessness affects promyelocytic multidrug resistance.

An immortalized promyelocytic cell line was studied to detect how doxorubicin uptake is affected by microgravity. The purpose of this experiment was to identify the effect that microgravity may have on multidrug resistance in leukocytes. HL60 cells and HL60 cells resistant to anthracycline (HL60/AR) were grown in RPMI and 10% FBS. Upon reaching orbit in the Space Shuttle Endeavour, the cells were robotically mixed with doxorubicin. Three days after mixing, cells were fixed with paraformaldehyde/glutaraldehyde. Ground control experiments were conducted concurrently using a robot identical to the one used on the Shuttle. Fixed cells were analyzed within 2 weeks of launch. Confocal micrographs identified changes in cell structure (transmittance), drug distribution (fluorescence), and microtubule polymerization (fluorescence). Flight cells showed a lack of cytoskeletal polymerization resulting in an overall amorphic globular shape. Doxorubicin distribution in ground cells included a large numbers of vesicles relative to flight cells. There was a greater amount of doxorubicin present in flight cells (85% +/- 9.7) than in ground control cells (43% +/- 26) as determined by image analysis. Differences in microtubule formation between flight cells and ground cells could be partially responsible for the differences in drug distribution. Cytoskeletal interactions are critical to the function of P-glycoprotein as a drug efflux pump responsible for multidrug resistance.

Biological Transport↗
PubMed1997

The influence of hyperbaric oxygenation on leukocyte viability and surface protein expression.

Hyperbaric oxygenation was studied as a potential inducer of cell growth and differentiation in promyelocytic leukemic HL60 cells. We studied changes in HL60 cells exposed to hyperbaric oxygen, oxygen, or carbon dioxide for 72 h. The proliferation rate and viability of cells in the hyperbaric oxygenation groups were significantly lower (p < 0.05) than for the controls. While CD13 and CD38 were expressed less following hyperbaric treatment, CD11b, CD14, and CD16 showed an increase following hyperbaric treatment, and CD10, CD15, and HLADR showed no change. These results support previous studies which demonstrate the role of oxygen tension in the regulation of cell cycle and protein expression.

Antigens, CD↗
PubMed1994

Human herpesvirus-6 infection in children. A prospective study of complications and reactivation.

BACKGROUND: Infection with human herpesvirus-6 (HHV-6) is nearly universal in infancy or early childhood. However, the course of this infection, its complications, and its potential for persistence or reactivation remain unclear. METHODS: We studied infants and children under the age of three years who presented to our emergency department with acute illnesses. Infants and young children without acute illness were studied as controls. HHV-6 infection was identified by blood-mononuclear-cell culture, serologic testing, and the polymerase chain reaction (PCR). RESULTS: No primary HHV-6 infection was found among 582 infants and young children with acute nonfebrile illnesses or among 352 controls without acute illness. Of 1653 infants and young children with acute febrile illnesses, 160 (9.7 percent) had primary HHV-6 infection, as documented by viremia and seroconversion. They ranged in age from 2 weeks to 25 months; 23 percent were under the age of 6 months. HHV-6 infections accounted for 20 percent of 365 visits to the emergency department for febrile illnesses among children 6 to 12 months old. Of the 160 infants and young children with acute HHV-6 infections, 21 (13 percent) were hospitalized, and 21 had seizures. Often the seizures appeared late and were prolonged or recurrent. HHV-6 infections accounted for one third of all febrile seizures in children up to the age of two years. In follow-up studies over a period of one to two years, the HHV-6 genome persisted in blood mononuclear cells after primary infection in 37 of 56 children (66 percent). Reactivation, sometimes with febrile illnesses, was suggested by subsequent increases in antibody titers in 16 percent (30 of 187) and by PCR in 6 percent (17 of 278). No recurrent viremia was detected. Of 41 healthy newborns studied, 12 (29 percent) had the HHV-6 genome in their blood mononuclear cells; nevertheless, 6 of these newborns subsequently had primary HHV-6 infections. CONCLUSIONS: In infants and young children HHV-6 infection is a major cause of visits to the emergency department, febrile seizures, and hospitalizations. Perinatal transmission may occur, with possible asymptomatic, transient, or persistent neonatal infection.

Acute Disease↗
PubMed1994

Reduced peak aerobic capacity in asymptomatic left ventricular systolic dysfunction. A substudy of the studies of left ventricular dysfunction (SOLVD). SOLVD Investigator. Studies of Left Ventricular Dysfunction.

BACKGROUND: Peak oxygen consumption is reduced in patients with symptomatic congestive heart failure, but functional capacity of patients with asymptomatic left ventricular systolic dysfunction has not been assessed by measurement of peak oxygen consumption attained during graded exercise testing. METHODS AND RESULTS: Peak oxygen consumption, that is, aerobic capacity (VO2, mL/kg per minute), was determined during graded treadmill exercise using the modified Naughton protocol in 40 patients with left ventricular systolic dysfunction (mean ejection fraction ranging from 14% to 35%; mean, 29%) who, while not receiving any cardiac medications, were totally asymptomatic, and in 41 age-matched normal subjects. Peak exercise duration and VO2 were significantly lower in patients with asymptomatic left ventricular systolic dysfunction than in normal subjects (948 +/- 273 versus 1239 +/- 372 seconds, P < .001, and 22.1 +/- 5.9 versus 29.8 +/- 7.7 mL/kg per minute, respectively, P < .001), while asymptomatic patients and normal subjects reached similar respiratory equivalents (1.14 +/- 0.11 versus 1.11 +/- 0.11 [NS]) and level of perceived exertion, using the modified Borg scale (7.4 +/- 2.6 versus 8.1 +/- 1.5 [NS]). Heart rate, systemic blood pressure, and oxygen pulse response to peak exercise were significantly lower in asymptomatic patients than in normal subjects. CONCLUSIONS: Although patients with left ventricular systolic dysfunction can be totally asymptomatic in their daily activities, they have experienced a substantial reduction in peak aerobic capacity when compared with normal subjects of similar age.

Aged↗
PubMed1993

Prediction of mortality and morbidity with a 6-minute walk test in patients with left ventricular dysfunction. SOLVD Investigators.

OBJECTIVE: To study the potential usefulness of the 6-minute walk test, a self-paced submaximal exercise test, as a prognostic indicator in patients with left ventricular dysfunction. DESIGN: Data were collected during a prospective cohort study, the Studies of Left Ventricular Dysfunction (SOLVD) Registry Substudy. SETTING: Twenty tertiary care hospitals in the United States, Canada, and Belgium. PARTICIPANTS: A stratified random sample of 898 patients from the SOLVD Registry who had either radiological evidence of congestive heart failure and/or an ejection fraction of 0.45 or less were enrolled in the substudy and underwent a detailed clinical evaluation including a 6-minute walk test. Patients were followed up for a mean of 242 days. OUTCOME MEASURES: Mortality and hospitalization. RESULTS: During follow-up, 52 walk-test participants (6.2%) died and 252 (30.3%) were hospitalized. Hospitalization for congestive heart failure occurred in 78 participants (9.4%), and the combined endpoint of death or hospitalization for congestive heart failure occurred in 114 walk-test participants (13.7%). Compared with the highest performance level, patients in the lowest performance level had a significantly greater chance of dying (10.23% vs 2.99%; P = .01), of being hospitalized (40.91% vs 19.90%; P = .002), and of being hospitalized for heart failure (22.16% vs 1.99%; P < .0001). In a logistic regression model, ejection fraction and distance walked were equally strong and independent predictors of mortality and heart failure hospitalization rates during follow-up. CONCLUSION: The 6-minute walk test is a safe and simple clinical tool that strongly and independently predicts morbidity and mortality in patients with left ventricular dysfunction.

Aged↗
PubMed1993

Assessment of quality of life as observed from the baseline data of the Studies of Left Ventricular Dysfunction (SOLVD) trial quality-of-life substudy.

The improvement of aspects of a patient's quality of life may be as important as prolonging survival in evaluating clinical trials of heart failure. The purpose of this study was to analyze the psychometric properties of the baseline measures from the quality-of-life substudy from the Studies of Left Ventricular Dysfunction (SOLVD) trial. The measures included the 6-Minute Walk Test, Dyspnea Scale, Living with Heart Failure, Physical Limitations, Psychologic Distress and Health Perceptions, as reported by both patients and staff. Cognitive functioning, such as Vocabulary, Digit Span and Trails Making, was also assessed. Patients were classified as New York Heart Association class I (n = 158) versus II or III (n = 150). The internal consistencies (i.e., reliabilities) of the self-report measures were high, except for the Health Perceptions of Class II or III patients. Reliability of the SOLVD quality-of-life battery was confirmed by significantly better life quality among New York Heart Association class I patients versus class II or III patients combined on the Walk Test, Physical Limitations, Dyspnea, Living with Heart Failure, Psychologic Distress and staff perceptions of patient health. In accordance with prior studies, the measures were uncorrelated with left ventricular ejection fraction. By demonstrating strong internal consistencies, reliability based on physician reports, and independence of ejection fraction levels, use of this quality-of-life assessment battery in this and other clinical trials of compromised ventricular functioning is supported.

Attitude to Health↗
PubMed1992

A noninvasive method of predicting pulmonary-capillary wedge pressure.

BACKGROUND: The noninvasive prediction of pulmonary-capillary wedge pressure (PCWP) is important for the recognition and treatment of a variety of cardiovascular disorders. The response of the arterial pressure to the Valsalva maneuver has been shown to correlate with the PCWP. We therefore devised a noninvasive method to measure this pressure response at the bedside and correlated these measurements with the PCWP measured directly with a pulmonary-artery catheter. METHODS: Simultaneous, blinded, noninvasive measurements of the ratio of the final amplitude to the initial amplitude of the pulse wave form during the stress phase of the Valsalva maneuver (pulse-amplitude ratio) and direct measurements of the PCWP were obtained in 20 clinically stable patients and in 14 clinically unstable patients who were receiving vasoactive agents, 12 of whom also had endotracheal tubes in place. RESULTS: Using linear regression analysis, we found that the pulse-amplitude ratio strongly correlated with the measured PCWP over a range of base-line values from 4 to 32 mm Hg for the 20 clinically stable patients (R2 = 0.80) and the 14 clinically unstable patients (R2 = 0.85). The method also correctly predicted changes in the PCWP after the administration of nitroglycerin or furosemide and after expansion of the intravascular volume (R2 = 0.79). CONCLUSIONS: These preliminary data indicate that a simple noninvasive method can accurately predict the PCWP and changes in the PCWP in response to medical therapy.

Blood Pressure↗
PubMed1992

Characteristics of peak aerobic capacity in symptomatic and asymptomatic subjects with left ventricular dysfunction. The Studies of Left Ventricular Dysfunction (SOLVD) Investigators.

Expired gas analysis was used to determine the aerobic exercise performance of subjects with depressed left ventricular (LV) systolic function and congestive heart failure (CHF). To determine whether subjects with no or minimal CHF have better aerobic exercise performance than do those with overt CHF, oxygen consumption (VO2) at anaerobic threshold (AT) and peak exercise was measured in 184 subjects with LV ejection fraction less than or equal to 0.35 who participated in the Studies of Left Ventricular Dysfunction. Subjects were divided into those with overt CHF needing treatment (treatment trial; n = 20) and those who had neither overt CHF nor treatment for CHF (prevention trial; n = 164). Treatment trial subjects had a lower LV ejection fraction (0.25 +/- 0.07) than did prevention trial ones (0.29 +/- 0.05; p = 0.001), but there were no differences in age, gender, body weight, resting heart rate and blood pressure. Treadmill exercise testing was performed after 2 to 3 weeks of placebo (no angiotensin-converting enzyme inhibitor) treatment. Treatment trial subjects exercised for a shorter time (493 +/- 160 seconds) and attained a lower peak VO2 (13 +/- 4 ml/kg/min) and VO2 at AT (11 +/- 4 ml/kg/min) than did prevention trial ones (842 +/- 277 seconds, and 20 +/- 6 and 16 +/- 5 ml/kg/min, respectively). Analysis of covariance showed that the differences in peak VO2 and VO2 at AT were statistically significant between the 2 trials after adjusting for age, gender, LV ejection fraction and New York Heart Association functional class.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Persistent chest pain following oral dipyridamole for thallium 201 myocardial imaging.

A patient was admitted to the hospital with acute chest pain. After acute myocardial infarction was ruled out, he underwent a stress thallium 201 scintigraphy using oral dipyridamole and developed persistent angina with ST-segment elevation. This complication has not been reported previously. It is recommended that appropriate intervention be available if severe ischemia develops following administration of dipyridamole for diagnostic imaging.

Angina Pectoris↗
PubMed1990

Carotid endarterectomy for chronic retinal ischemia.

Carotid arterial disease may result in a variety of ischemic ocular problems that can eventually lead to permanent blindness. From 1984 to 1988, 18 patients underwent reconstruction of the carotid artery in an attempt to restore normal retinal arterial flow and, thereby, reverse or prevent progression of ischemic oculopathy. During a mean period of 21 months after carotid arterial reconstruction, subjective improvement in vision as well as a resolution in eye and periorbital pain was reported in 87.5 per cent of the patients. Measured visual acuity improved or stabilized in 94.4 per cent; macular photostress recovery times improved in 87.5 per cent, funduscopic examinations noted improvement or resolution in ischemic signs in 93.3 per cent and intraocular pressures improved in two of three patients. One patient experienced recurrent episodes of amaurosis fugax, which resolved after two weeks and did not recur. A second patient experienced an increase in intraocular pressures with visual deterioration, required laser photocoagulation after which the condition of the patient stabilized but only after significant visual impairment. Carotid arterial reconstruction is effective for the treatment of ischemic oculopathy and is most beneficial if performed early, before the onset of irreversible neovascular glaucoma.

Aged↗