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Biomedical subjects

L Horowitz

Publications and source records attributed to L Horowitz.

At least 19 recordsLinked to original sources
PubMed2006

The global atmospheric environment for the next generation.

Air quality, ecosystem exposure to nitrogen deposition, and climate change are intimately coupled problems: we assess changes in the global atmospheric environment between 2000 and 2030 using 26 state-of-the-art global atmospheric chemistry models and three different emissions scenarios. The first (CLE) scenario reflects implementation of current air quality legislation around the world, while the second (MFR) represents a more optimistic case in which all currently feasible technologies are applied to achieve maximum emission reductions. We contrast these scenarios with the more pessimistic IPCC SRES A2 scenario. Ensemble simulations for the year 2000 are consistent among models and show a reasonable agreement with surface ozone, wet deposition, and NO2 satellite observations. Large parts of the world are currently exposed to high ozone concentrations and high deposition of nitrogen to ecosystems. By 2030, global surface ozone is calculated to increase globally by 1.5 +/- 1.2 ppb (CLE) and 4.3 +/- 2.2 ppb (A2), using the ensemble mean model results and associated +/-1 sigma standard deviations. Only the progressive MFR scenario will reduce ozone, by -2.3 +/- 1.1 ppb. Climate change is expected to modify surface ozone by -0.8 +/- 0.6 ppb, with larger decreases over sea than over land. Radiative forcing by ozone increases by 63 +/- 15 and 155 +/- 37 mW m(-2) for CLE and A2, respectively, and decreases by -45 +/- 15 mW m(-2) for MFR. We compute that at present 10.1% of the global natural terrestrial ecosystems are exposed to nitrogen deposition above a critical load of 1 g N m(-2) yr(-1). These percentages increase by 2030 to 15.8% (CLE), 10.5% (MFR), and 25% (A2). This study shows the importance of enforcing current worldwide air quality legislation and the major benefits of going further. Nonattainment of these air quality policy objectives, such as expressed by the SRES-A2 scenario, would further degrade the global atmospheric environment.

Air Pollutants↗
PubMed2001

Mental health aspects of emergency medical services for children: summary of a consensus conference.

OBJECTIVE: To address the mental health needs of children involved in emergency medical services (EMS). METHODS: A multidisciplinary consensus conference convened to identify mental health needs of children and their families related to pediatric medical emergencies, to examine the impact of psychological aspects of emergencies on recovery and satisfaction with care, and to delineate research questions related to mental health aspects of medical emergencies involving children. RESULTS: The consensus group found that psychological and behavioral factors affect physical as well as emotional recovery after medical emergencies. Children's reactions are critically affected by age and developmental level, characteristics of the emergency medical event, and parent reactions. As frontline health care providers, EMS staff members are in a pivotal position to recognize and effectively manage the mental health needs of patients and their families. CONCLUSIONS: Ecological changes in emergency departments, such as linkages to mental health follow-up services, training of EMS providers and mental health professionals, and focused research that provides an empirical basis for practice, are necessary components for improving current standards of health care.

Adaptation, Psychological↗
PubMed2001

Mental health aspects of emergency medical services for children: summary of a consensus conference.

OBJECTIVE: To address the mental health needs of children involved in emergency medical services (EMS). METHODS: A multidisciplinary consensus conference convened to identify mental health needs of children and their families related to pediatric medical emergencies, to examine the impact of psychological aspects of emergencies on recovery and satisfaction with care, and to delineate research questions related to mental health aspects of medical emergencies involving children. RESULTS: The consensus group found that psychological and behavioral factors affect physical as well as emotional recovery after medical emergencies. Children's reactions are critically affected by age and developmental level, characteristics of the emergency medical event, and parent reactions. As frontline health care providers, EMS staff members are in a pivotal position to recognize and effectively manage the mental health needs of patients and their families. CONCLUSIONS: Ecological changes in emergency departments, such as linkages to mental health follow-up services, training of EMS providers and mental health professionals, and focused research that provides an empirical basis for practice, are necessary components for improving current standards of health care.

Adolescent↗
PubMed2001

A comparison of ON-PUMP vs OFF-PUMP coronary artery bypass surgery among low, intermediate, and high-risk patients: the Hartford Hospital experience.

BACKGROUND: Off-pump coronary artery bypass (OP-CAB) graft surgery is being used with increasing frequency. This study was designed to compare OP-CAB outcomes with conventional surgical revascularization using cardiopulmonary bypass (CPB) in patients with varying risk categories at a high-volume center. METHODS AND RESULTS: Between 1/1/1999 and 1/31/2001, bypass surgery was performed on 1,312 patients, including 348 OP-CAB cases and 964 CPB cases. Compared to CPB cases, OP-CAB patients were more likely to be female and had a lower incidence of three vessel coronary artery disease, prior percutaneous intervention, and prior bypass surgery. Postoperatively, OP-CAB patients had a lower incidence of renal failure and prolonged ventilatory support, as well as a lower composite endpoint of inhospital mortality, perioperative myocardial infarction, cerebrovascular accident, and/or renal failure. In addition, OP-CAB patients required fewer transfusions and had a shorter total length of hospital stay. In general, morbidity and mortality increased in both OP-CAB and CPB groups with increasing Parsonnet score. CONCLUSIONS: OP-CAB surgery is a safe and effective alternative to conventional coronary artery bypass graft (CABG) surgery, with a lower incidence of major in-hospital adverse clinical events and a decreased requirement for medical resources. Adverse OP-CAB outcomes correlate well with pre-operative Parsonnet Score.

Aged↗
PubMed1998

Characterization of topotecan-mediated redistribution of DNA topoisomerase I by digital imaging microscopy.

Topographical image measures have been used to characterize the subnuclear distribution of DNA topoisomerase I in human tumor cell lines. This topographical analysis allowed a mathematical description of staining patterns to be produced that did not depend on subjective grading. The redistribution of topoisomerase I in response to increasing concentrations of topotecan was then monitored by this method. The cell lines were stained for topoisomerase I by indirect immunofluorescence methods. Digital imaging microscopy and image analysis were used to extract the nucleus from each cell, and nine parameters describing the topography of the distribution of topoisomerase I within the nucleus were computed for each. Use of multivariate analysis of variance enabled this nine-parameter set to be reduced to a single canonical variable, representing 60-90% of the observed internuclear variance. Plotting the canonical variable vs drug concentration resulted in dose-response curves that could be fitted well by a simple Emax model. From these curve fits, EC50 and Emax values for drug-induced redistribution of topoisomerase I were determined. Our results indicate that neither the maximum extent of topoisomerase I redistribution (Emax) nor the EC50 for drug-induced redistribution correlated well with the growth inhibition produced by continuous exposure to topotecan in these cell lines. However, the EC50 determined for the 1-h high-concentration exposure did reflect the growth inhibition produced in cells exposed to the drug for 1 h. The methodology described may also be generally applied to any antigen of interest.

Biological Transport↗
PubMed1994

Acute asthma. Single dose oral steroids in paediatric community clinics.

The treatment of an acute asthma attack usually includes bronchodilators and often steroids. We studied 70 children who were randomly assigned to receive either single dose steroids (oral prednisone: 20-40 mg) or placebo on a double blind basis. The time course of the observation was 72 h. We demonstrate that a single dose of steroids, given orally in paediatric community clinics during an acute mild to moderate asthma attack, significantly improves the patient's course; deterioration was prevented, symptoms were relieved faster, and hospitalization was not required. We encourage paediatricians in the ambulatory clinics to follow this treatment modality and to give, in addition to other conventional therapy, a single oral dose of steroids early in the asthma attack, in order to relieve and shorten the child's distress.

Acute Disease↗
PubMed1994

Release of atrial natriuretic peptide in brief ischemia-reperfusion in isolated rat hearts.

We studied the effects of short-term global ischemia and reperfusion on ANP secretion from Langendorff-perfused rat hearts compared with isolated ventricles. Effects of regional ischemia, with or without increased atrial pressure, were examined in Langendorff-perfused and working heart models. Five minutes of global ischemia were associated with elevated levels of atrial natriuretic peptide (ANP) in the coronary effluent immediately and for approximately 10 min after resumption of reperfusion, resulting in a net hormone excess of 23 +/- 5 ng/g wet wt. The ventricles produced on the average 11% ANP compared with the whole heart, and their contribution of to postischemic ANP overflow was approximately proportional to their basal production. In Langendorff-perfused hearts, regional ischemia increased the concentration of ANP in the coronary effluent 51 +/- 11%, whereas the secretion rate (per minute) decreased 18 +/- 5%. In the presence of atrial distension in the working heart model, a trend for increase in ANP secretion was apparent. We conclude that global ischemia, even of brief duration, has an independent stimulatory effect on ANP release, the ischemic atrium being responsible for most of the excess. Regional ischemia, when not accompanied by atrial distention, reduces the ANP secretion rate during the ischemic period. Heart failure secondary to ischemia stimulates ANP secretion, but this response seems to be both delayed and attenuated compared with atrial stretch alone.

Animals↗
PubMed1992

Video display terminal operation: a potential risk in the etiology and maintenance of temporomandibular disorders.

Surveys indicate over 50 million Americans, mostly women, currently operate video display terminals (VDTs) at home or in the workplace. Recent epidemiological studies reveal more than 75% of approximately 30 million American temporomandibular disorder (TMD) sufferers are women. What does the VDT and TMD have in common besides an affinity for the female gender? TMD is associated with numerous risk factors that commonly initiate sympathetic nervous system and stress hormone response mechanisms resulting in muscle spasms, trigger point formation, and pain in the head and neck. Likewise VDT operation may be linked to three additional sympathetic nervous system irritants including: (1) electrostatic ambient air negative ion depletion, (2) electromagnetic radiation, and (3) eyestrain and postural stress associated with poor work habits and improper work station design. Additional research considering the roles these three factors may play in the etiology of TMD and other myofascial pain problems is indicated. Furthermore, dentists are advised to educate patients as to these possible risks, encourage preventive behaviors on the part of employers and employees, and recommend workplace health, safety, and ergonomic upgrades when indicated.

Air Ionization↗
PubMed1992

Effects of captopril on metabolic and hemodynamic alterations in global ischemia and reperfusion in the isolated working rat heart.

In the isolated working rat heart model, we studied metabolic and hemodynamic effects of 5- and 30-min global ischemia followed by reperfusion and assessed the potentially beneficial effect of captopril 80 micrograms/ml added throughout the experiment. Creatine kinase (CK) and catecholamines were measured in coronary effluent. De novo eicosanoids (prostaglandin E2) synthesis was assessed in endocardial explants. Hemodynamic alterations occurred after 30-min ischemia and were reflected most dramatically by a reduction in cardiac output (CO 72 +/- 10% of baseline values in captopril vs. 68 +/- 16% in controls) without significant differences as a result of treatment. Captopril shortened reperfusion ventricular fibrillation (VF) duration (6.9 +/- 1.2 vs. 13.6 +/- 8.7 min, p less than 0.05) but had no effect on VF incidence. No differences occurred in norepinephrine (NE) outflow, whereas total CK release was greater in controls. Five controls versus none of the treated hearts (p less than 0.05) released trace amounts of epinephrine during reperfusion. Increased de novo PGE2 synthesis was demonstrated after 5-min I (465 +/- 168 vs. 238 +/- 75 pg/100 mg tissue per hour, p less than 0.01). Captopril stimulated production of PGE2 in normoxic hearts (p less than 0.02), but the difference was no more apparent in ischemic hearts. We conclude that captopril produces some biochemical and electrophysiologic evidence of myocardial salvage, but these effects are not sufficient to induce hemodynamic improvement after global ischemia and reperfusion.

Animals↗
PubMed1988

Development of prone extension postures in healthy infants.

The purposes of this study were to 1) investigate the sequence of development of head, upper extremity, and lower extremity extension in the prone extension posture in healthy infants; 2) identify the variations in the sequence; and 3) compare these postures within the sequence with the development of prone-on-elbows and prone-on-hands postures. Twenty healthy, full-term infants were observed longitudinally from 8 to 28 weeks of age. Two of the infants could not complete the study, and two infants never used the prone extension posture. The data from 16 of the infants, therefore, were analyzed. The results indicate that the sequence of development of the prone extension posture consists of head extension, followed by lower extremity extension, and then upper extremity extension. The results also indicate that upper extremity extension in the prone extension posture does not appear to be a prerequisite for the prone-on-elbows or prone-on-hands postures. These findings suggest that infants may use different strategies for developing motor control in the head and lower extremities than in the upper extremities. This information adds to our knowledge of the normal developmental process and may have significance in the planning of physical therapy programs.

Arm↗
PubMed1985

A comparative study of the electrophysiologic effects of Striadyne, adenosine triphosphate and adenosine in the canine heart.

The chronotropic and dromotropic effects of the intra-atrial administration of 0.97, 1.93 and 2.90 microM/kg Striadyne, the pharmaceutical form of adenosine triphosphate (ATP) for clinical use, ATP, and adenosine, were compared in 13 anesthetized dogs. Striadyne, ATP and adenosine exerted transient dose-dependent negative chronotropic and dromotropic effects. There was no significant difference between the electrophysiologic effects of Striadyne and ATP which were significantly more pronounced than those of adenosine. Atropine (0.2 mg/kg) significantly attenuated the electrophysiologic effects of 2.90 microM/kg Stridyne and ATP but not those of adenosine. It is concluded that Striadyne and ATP have similar electrophysiologic effects which are more pronounced than those of adenosine mainly due to vagal involvement in their mechanism of action.

Adenosine↗
PubMed1982

Alimentary tract involvement in Kaposi sarcoma: radiographic and endoscopic findings in 25 homosexual men.

An outbreak of Kaposi sarcoma has recently occurred among young homosexual men. It differs from the classic form in its virulence and preponderance of systemic manifestations. Twenty-five homosexual men with a mean age of 37 and biopsy-proven Kaposi sarcoma received extensive gastrointestinal evaluations. Twelve patients (48%) had evidence of gastrointestinal involvement by radiography and/or endoscopy. Lesions were found in the larynx, oropharynx, esophagus, stomach, duodenum, and colon. Radiographically they ranged from minimally elevated submucosal lesions, some with central ulceration, to polypoid defects. Abdominal CT was obtained in 18 patients, 11 of whom showed abnormalities. Of those with abnormal CT, 50% had retroperitoneal adenopathy. The gastrointestinal radiographic findings with endoscopic correlation in this unusual group of patients is discussed.

Adult↗