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Biomedical subjects

K Lurie

Publications and source records attributed to K Lurie.

12 recordsLinked to original sources
PubMed1995

Characterization of subcutaneous microvascular blood flow during tilt table-induced neurally mediated syncope.

OBJECTIVES: This study aimed to characterize subcutaneous blood flow changes during neurally mediated syncope and to determine whether microvasculature oscillation (vasomotion) is characteristically altered in conjunction with syncopal events. BACKGROUND: Marked pallor is commonly associated with neurally mediated syncope. However, little attention has been paid to the evaluation of subcutaneous blood flow and vasomotion in this setting. METHODS: This study utilized laser Doppler flowmetry to assess changes in subcutaneous microvascular blood flow during head-up tilt table testing in 13 patients with syncope and 6 control subjects. Blood flow and vasomotion frequency were measured continuously before, during and after completion of 80 degrees head-up tilt testing (< or = 25-min duration). RESULTS: Among the 13 patients with syncope, tilt testing reproduced syncopal symptoms in 9 (tilt-positive group) but not in 4 (tilt-negative group). None of the six control subjects developed symptoms during testing. Baseline mean subcutaneous blood flow did not differ significantly among the three groups. However, during upright tilt, blood flow gradually diminished in the tilt-positive group, reaching a nadir of 0.8 +/- 0.33 ml/min per 100 g of tissue (mean +/- SD), but remained relatively constant in the tilt-negative group and control subjects. The difference in mean blood flow response to tilt was statistically significant when the tilt-positive group was compared with either the tilt-negative group or control subjects (p < 0.001). Similarly, baseline blood flow oscillation frequency did not differ significantly in the three subgroups (tilt-positive group 0.2 +/- 0.11 Hz; tilt-negative group 0.2 +/- 0.02 Hz; control subjects 0.2 +/- 0.11 Hz). Subsequently, during tilt testing only the tilt-positive group exhibited increased oscillation frequency; oscillation frequency remained essentially constant throughout the tilt test in the tilt-negative group and control subjects (p < 0.001, tilt-positive group vs. either the tilt-negative group or control subjects). CONCLUSIONS: These findings document an expected diminution of subcutaneous blood flow in association with neurally mediated syncope and indicate that characteristic changes in microvasculature oscillation frequency occur in conjunction with syncopal symptoms. To the extent that microvasculature vasomotion is influenced by neural control, the changes in vasomotion frequency are consistent with relative diminution of peripheral sympathetic neural influence during neurally mediated syncopal episodes.

Adolescent↗
PubMed1994

Multiple-sensor systems for physiologic cardiac pacing.

PURPOSE: To review the status of artificial sensors in cardiac pacemakers and the rationale for developing pacing systems that use multiple sensors. DATA SOURCES: Journal articles published between 1982 and 1993 indexed in MEDLINE using the keywords pacemakers, sensors, and rate-adaptive, as well as abstracts and articles in the authors' personal files. STUDY SELECTION: Articles describing clinical experience with or clinical evaluation of cardiac pacing systems using multiple artificial sensors. DATA SYNTHESIS: Artificial sensors were created to adjust pacing rate reliably in response to changes in levels of physical exertion for patients with sinoatrial disease in whom exercise heart rate response is inadequate (for example, chronotropic incompetence in sinoatrial disease). To achieve this, various artificial sensors were developed and many reports confirm improved exertional tolerance. More recently, sensors have assumed a greater role in cardiac pacemakers. For example, sensors are used to permit automatic adjustment of certain programmable pacemaker settings, such as the atrioventricular interval. In the future, they may also be used to maximize pacemaker longevity by automatically optimizing energy output (voltage, pulse width). No single sensor is ideal for all potential applications, and investigators have advocated using two or more sensors. Several pacemakers that use multiple sensors with different but complementary operating characteristics are already commercially available outside the United States. Although preliminary findings are encouraging, additional clinical experience with these pacemakers is needed to determine their ultimate role in clinical practice. CONCLUSION: Simultaneous use of multiple complementary artificial sensors may permit development of cardiac pacemakers that operate more physiologically yet require less specialized medical follow-up.

Clinical Trials as Topic↗
PubMed1993

Head-up tilt testing with and without isoproterenol infusion in healthy subjects of different ages.

Passive head-up tilt testing with or without infusion of isoproterenol is used in the investigation and management of patients with syncope. Twenty-five healthy asymptomatic volunteers prospectively grouped according to age (young [28 +/- 1.7 years]: n = 9; middle [51 +/- 3.3 years]: n = 11; elderly [81 +/- 2.4 years]: n = 5; mean +/- SE) were studied during: (1) supine carotid sinus massage; (2) 60 degrees head-up tilt alone; and (3) infusion of isoproterenol to raise the heart rate 20% above supine baseline, prior to 10-minute repeat tilt. Symptoms occurred in three subjects (12%) and only occurred with passive tilting alone. Two young subjects had syncope with sinus pauses greater than 10 seconds. One elderly subject developed atrial flutter. No subject had symptoms or hypotension during tilt plus isoproterenol or a pause greater than 3 seconds with carotid sinus massage. With passive tilt, mean heart rate increased by 16 +/- 6 beats/min and 18 +/- 7.8 beats/min in the young and middle aged subjects (P < 0.05), but only by 6 +/- 5 beats/min in the elderly (P = NS, supine vs 60 degrees in each group). With head-up tilt plus isoproterenol infusion, the mean heart rate elevation in response to tilt was 17 +/- 9 beats/min, 8 +/- 3 beats/min, and 12 +/- 4 beats/min for the young, middle, and elderly subjects, respectively (P < 0.05, supine vs 60 degrees in each group).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Improved treatment of intra-abdominal abscess. A result of improved localization, drainage, and patient care, not technique.

Outcome in patients with abdominal abscesses treated at the University of Pennsylvania, Philadelphia, between 1973 and 1978 (group 1) was compared with that in patients treated between 1981 and 1986 (group 2). Mortality was less in group 2 patients (21% vs 39% in group 1). The decrease in mortality in group 2 was accompanied by a greater percentage of successful predrainage localization (74% vs 55% in group 1), successful initial drainage (76% vs 55% in group 1), and decreased predrainage organ failure (23% vs 52% in group 1). Because failure of initial drainage and predrainage organ failure were associated with increased mortality, improvement in both of these criteria contributed substantially to the lower mortality in group 2 patients. There were no differences in mortality, in initial success in drainage, or in length of hospital stay when 29 group 2 patients who underwent percutaneous drainage were compared with 37 patients who underwent surgical drainage. Mortality (22% vs 21%) and initial success (78% vs 72%) were similar for patients who underwent surgical and percutaneous drainage, respectively. We conclude that initial success in localization and drainage of the abscess is more important than whether drainage is surgical or percutaneous.

Abdomen↗
PubMed1987

Enhancement of survival and proliferation of clonogenic cells by monocyte-derived growth factors.

Human peripheral blood monocytes release a factor that enhances the clonal growth of human epithelial tumor cells in soft agar. The monocyte-derived growth factor was needed for both cellular proliferation and survival. Survival of SW-13 colony-forming cells decreased linearly in the absence of monocyte-conditioned media (MO-CM). Cells failed to respond to MO-CM after four days in culture. Although MO-CM enhanced growth when cells were plated at low density, growth was also enhanced when cell density was not a limiting factor. MO-CM increased DNA synthesis of SW-13 cells growing in monolayer culture as measured by tritiated-thymidine incorporation. These findings support evidence indicating inflammatory products may play a role in maintenance of the transformed phenotype.

Adrenal Cortex Neoplasms↗
PubMed1987

Intra-abdominal abscess in the 1980s.

Prompt recognition, early localization, and adequate drainage have contributed to the decreased morbidity and mortality rates associated with intra-abdominal abscess in the last decade. The physical examination, ultrasonography, computed tomography, and radionuclide scans provide information that leads to early detection and localization of abscess in almost all patients. Percutaneous drainage should be the initial procedure unless specific indications for surgery exist.

Abdomen↗
PubMed1986

Monocyte-derived growth factors for human tumor clonogenic cells.

Human peripheral blood monocytes secrete a soluble factor that enhances the ability of human epithelial tumor cell lines to clone in soft agar. Monocytes increased colony growth in a concentration-dependent manner, although inhibition of cell growth was observed in the presence of high concentrations of monocytes. Addition of indomethacin to monocytes did not abrogate this inhibition. Exposure of monocytes to endotoxin increased their ability to secrete stimulatory factors. Nonadherent lymphocytes were unable to support colony growth. Conditioned media from unstimulated monocytes also increased colony growth. Growth-promoting activity was detected in the media within the first 24 hr of culture, reaching a peak at 72 hr. Activity was not observed in monocyte lysates. Monocytes released this activity when cultured in the presence of both serum-free and serum-containing media. The activity was nondialyzable, relatively heat stable, and failed to adhere to CM-Sephadex. The demonstration of a monocyte-derived factor that enhances growth of epithelial tumor colonies supports findings indicating that inflammatory products may enhance tumor cell growth in vitro.

Adenocarcinoma↗
PubMed1982

Decreased catecholamine sensitivity and beta-adrenergic-receptor density in failing human hearts.

To identify the role of the myocardial beta-adrenergic pathway in congestive heart failure, we examined beta-adrenergic-receptor density, adenylate cyclase and creatine kinase activities, muscle contraction in vitro, and myocardial contractile protein levels in the left ventricles of failing and normally functioning hearts from cardiac-transplant recipients or prospective donors. Eleven failing left ventricles had a 50 to 56 per cent reduction in beta-receptor density, a 45 per cent reduction in maximal isoproterenol-mediated adenylate cyclase stimulation, and a 54 to 73 per cent reduction in maximal isoproterenol-stimulated muscle contraction, as compared with six normally functioning ventricles (P less than 0.05 for each comparison). In contrast, cytoplasmic creatine kinase activity, adenylate cyclase activities stimulated by fluoride ion and by histamine, histamine-stimulated muscle contraction, and levels of contractile protein were not different in the two groups (P less than 0.05). We conclude that in failing human hearts a decrease in beta-receptor density leads to subsensitivity of the beta-adrenergic pathway and decreased beta-agonist-stimulated muscle contraction. Regulation of beta-adrenergic receptors may be an important variable in cardiac failure.

Adenylyl Cyclases↗