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Biomedical subjects

L Lopez

Publications and source records attributed to L Lopez.

At least 55 records · Page 3Linked to original sources
PubMed1997

An invitational workshop on collaboration between quality improvement organizations and business coalitions.

BACKGROUND: The center for Clinical Quality Evaluation, in conjunction with The American Health Quality Association, Midwest Business Group on Health, National Business Coalition on Health, and the funder, the Agency for Health Care Policy and Research, conducted an invitational workshop January 14-15, 1997, in Washington, DC. A select group of federally designated peer review/quality improvement organizations (QIOs)--organizations that work at the local level to improve and promote the health status of Medicaid and Medicare beneficiaries--and business coalitions from nine states met to discuss public/private collaboration on community-based quality improvement projects. WORKSHOP AGENDA: The 1 1/2-day sessions included a keynote address by Chris Queram, MA, chief executive officer of the Employer Health Care Alliance, Madison, Wisconsin, who provided background and context on the principles of community-based collaboration; a presentation on an advanced QIO/business coalition collaborative case study by HealthInsight, Inc (the Utah QIO), and Business/Health Partnership (the Salt Lake City business coalition); a case study on a beginning QIO/business coalition collaborated by the Health Accountability Foundation, a partnership between IPRO (the New York State QIO) and the New York Business Group on Health (the New York City business coalition); small group breakout sessions, where participants from each state/local community and Washington, DC-based health associations and specialty societies met to identify common goals and opportunities to collaborate; report on the progress made by each small group; and discuss future plans for collaborating on quality improvement projects. CONCLUSIONS: Many of the participating QIOs and business coalitions have already begun collaborating on quality improvement projects.

Cooperative Behavior↗
PubMed1997

Glucose availability and the electrophysiology of the human visual system.

Glucose is a main energy source to neurons in brain (with limited storage capability) and retina (where it is stored in glial Müller cells and supplied upon demand). Glucose availability and visual function are related. Human positron emission tomography studies indicate increased blood flow and glucose metabolic rate in primary visual cortex during stimulation, with retinotopic distribution. Retinal electrophysiology covaries with glucose concentration in in vitro models as well as in humans, at comparable concentrations in the physiological range. The interactions between retinal electrophysiology (notably the electroretinogram b-wave) and glucose metabolism appear more stringent than for cortical evoked responses. K-channels regulated by intracellular ATP are thought to link neuron excitability (and electrophysiological activity) on the metabolic state. High-affinity sulphonylurea binding sites for K-channels are widely distributed in brain. K-channels conceivably modulate neurotransmitter release and are inactivated by elevated glucose concentrations and sulfonylurea drugs used to treat diabetes.

Electroretinography↗
PubMed1996

Breast cancer and lactation history in Mexican women.

The authors conducted a case-control study in Mexico City between September 1990 and December 1992 to determine whether a dose-response relation could be observed between duration of lactation and the risk of breast cancer. Cases, women aged 20-75 years, were identified through six hospitals in Mexico City (n = 349) and were interviewed to obtain data on risk factors for breast cancer, including a detailed history of lactation. Controls (n = 1,005) were selected from the general population using the Mexican national sampling frame. Parous women who had ever lactated had a reduction in breast cancer risk (age-adjusted odds ratio (OR) = 0.39, 95% confidence interval (CI) 0.25-0.62). A small decreasing trend of breast cancer risk in relation to duration of lactation (p < 0.001) was observed. Compared with parous women who had never breast-fed, women who had breast-fed for 12-24 months had an age-adjusted odds ratio of 0.47 (95% CI 0.27-0.83). A stronger protective effect was observed with lactation duration for the first live birth among pre- and postmenopausal women (for 4-12 months of lactation, OR = 0.56 (95 percent CI 0.32-0.96) and OR = 0.48 (95 percent CI 0.29-0.81) in pre- and postmenopausal women, respectively). Adjusting for potentially confounding factors modified these results only slightly. The declining trend in fertility and lactation among Mexican women could lead to a major epidemic of breast cancer such as that observed in Western countries.

Adult↗
PubMed1996

A neuromagnetic study of movement-related somatosensory gating in the human brain.

Neuromagnetic fields from the left cerebral hemisphere of five healthy, right-handed subjects were investigated under three different experimental conditions: (1) electrical stimulation of the right index finger (task S); (2) voluntary movement of the same finger (M); (3) M+S condition, consisting of voluntary movements of the right index finger triggering the electrical stimulus at the very beginning of the electromyogram. The three conditions were administered in random order every 5-8 s. In addition, the task somatosensory evoked fields (task SEFs) gathered during condition (1) were compared with control SEFs recorded at the beginning of the experiment during rest. In all subjects the overlay of somatosensory stimulation on movement provoked a decrement in brain responsiveness (gating) as determined by the amplitude of gated SEFs. The latter was found as the difference between the neuromagnetic fields during M+S condition (overlaying of movement and sensory stimulation) minus neuromagnetic fields under M condition (M only). The gating effect was found to begin approximately 30 ms after movement onset, and to last for the whole period of the ongoing movement. The theoretical locus of gating was estimated by dipole localisation of the difference between task SEFs and gated SEFS using a moving dipole model. The site of the "early" gating effect (< 40 ms) was found to be more anteriorly located than the "later" (> 40 ms) gating effect. The task SEFs were found to be larger (significant after 30 ms) than the control SEFs elicited under the basal condition. The results are discussed with respect to timing, mechanism (centrifugal and centripetal), locus and selectivity of gating. In addition, the results are discussed with regard to clinical application (measuring attentional deficits in patients with impairments of higher mental functions and measuring gating deficits in patients with disturbed sensorimotor integration.

Adult↗
PubMed1996

Combination of ondansetron and droperidol in the prophylaxis of postoperative nausea and vomiting.

The aim of this study was to compare the efficacy and safety of ondansetron plus droperidol with each drug alone or placebo in the prevention of postoperative nausea and vomiting (PONV). One hundred females, aged 18-65 yr, ASA physical status I-II, undergoing general anesthesia for elective abdominal surgery were included in a prospective, double-blind, placebo-controlled, randomized study. A standardized anesthetic technique and postoperative analgesia (ketorolac plus patient-controlled analgesia [PCA] with morphine) were used in all patients. Patients were randomly assigned to receive placebo (Group 1, n = 25), droperidol 2.5 mg with induction of anesthesia and 1.25 mg 12 h later (Group 2, n = 25), ondansetron 4 mg with induction (Group 3, n = 25), and ondansetron plus droperidol at the same doses as Groups 3 and 2, respectively (Group 4, n = 25). A complete response, defined as no PONV in 48 h, occurred in 28% of patients in Group 1, 60% in Group 2 (P < 0.05 vs Group 1), 56% in Group 3 (P < 0.05 vs Group 1), and 92% in Group 4 (P < 0.01 vs Groups 1, 2, and 3). Sedation was significantly greater with droperidol (Groups 2 and 4) for 12 h postoperatively. In conclusion, the combination of ondansetron plus droperidol was more effective than each antiemetic alone or placebo in the prevention of PONV in women undergoing elective abdominal surgery.

Adolescent↗
PubMed1995

Single fiber electromyography of extraocular muscles: a sensitive method for the diagnosis of ocular myasthenia gravis.

We performed single fiber electromyography (SFEMG) in the superior rectus and levator palpebralis (SR-LP) muscles of 17 patients with pure ocular myasthenia gravis (MG) and 9 controls. Thirteen patients were also assessed with SFEMG in the orbicularis oculi (OO) muscle. All the MG patients but none of the control subjects showed abnormal SFEMG jitter in the SR-LP muscles. On the other hand, only 62% of the MG patients had abnormal SFEMG jitter in the OO muscle. The procedure was well tolerated by the patients, and complications were minor. We conclude that SFEMG of the SR-LP muscles is a safe and highly sensitive technique for the diagnosis of ocular MG.

Adult↗
PubMed1995

Scalp-recorded oscillatory potentials evoked by transient pattern-reversal visual stimulation in man.

Replicable oscillatory potentials, time-locked to pattern stimuli (9.0 degrees central; counterphase reversal at 2.13 Hz) were dissociated from conventional, broad-band VEPs recorded in healthy volunteers at occipital scalp locations by high-pass digital filtering at 17.0-20.0 Hz. Nine consecutive wavelets were identified with a 56.4 +/- 8.4 msec mean latency of the first replicable wavelet and mean peak-to-peak amplitude varying between 0.9 and 2.0 muV. The first 2 wavelets had significantly shorter latencies than wave N70 of unfiltered VEP, whereas the last 2 wavelets had longer latencies than N145. Latency and amplitude values varied as a function of contrast and spatial frequency of the stimulus, with shorter latencies and larger amplitudes at 60-90% contrast level and tuning of amplitude at 5.0 c/deg. All wavelets were correlated with wave P100 of unfiltered VEP, while a correlation with N70 of VEP was observed only for those wavelets with latencies in the range of wave P100. Two patients with documented brain lesions involving the visual system are described as examples of oscillatory responses occurring irrespective of filter bandpass and instead of the expected conventional VEP when the generation of these is interfered with by brain pathology. A substantial cortical contribution to the origin of the oscillatory response is conceivable. It is suggested that the oscillatory response to pattern-reversal stimulation reflects events in the visual system that are parallel to, and partly independent of, the conventional VEP, with potential application in research or for clinical purposes.

Adolescent↗
PubMed1995

Neuroendocrine cells in peripheral prostatic zone: age, prostatic intraepithelial neoplasia and latent cancer-related changes.

The neuroendocrine cells (NCs) in the peripheral prostatic zone of 32 patients without prostatic symptoms and with an average age of 61.4 +/- 6.7 (range 48-75) years were studied, and it was found that most are closed-type cells (95.8%) and that there is a gradual fall both in their total number and the number per square millimeter (p = 0.03) with advancing age. There were microscopic foci of high-grade prostatic intraepithelial neoplasia (PIN) in 59.3% of the patients and occult carcinomas in 28.1%, but no statistical relationship was found between these lesions and the number of NCs (p = 0.35 and p = 0.9, respectively). The gradual increase in NCs in the peripheral zone of normal prostates as of adolescence, reported in the literature, would appear to support a possible androgenic action on these cells. Our finding of a decrease in patients with foci of PIN and carcinoma from the fifth decade suggests that this decrease in NCs may make the prostate more susceptible to carcinogenic factors.

Adenocarcinoma↗
PubMed1995

Environmental urban lead exposure and blood lead levels in children of Mexico City.

Lead contamination is now a leading public health problem in Mexico. However, there are few data on the lead content of various environmental sources, and little is known about the contribution of these sources to the total lead exposure in the population of children residing in Mexico City. We conducted a cross-sectional study in a random sample of 200 children younger than 5 years of age who lived in one of two areas of Mexico City. Environmental samples of floor, window, and street dust, paint, soil, water, and glazed ceramics were obtained from the participants' households, as well as blood samples and dirt from the hands of the children. Blood lead levels ranged from 1 to 31 micrograms/dl with a mean of 9.9 micrograms/dl (SD 5.8 micrograms/dl). Forty-four percent of the children 18 months of age or older had blood lead levels exceeding 10 micrograms/dl. The lead content of environmental samples was low, except in glazed ceramic. The major predictors of blood lead levels were the lead content of the glazed ceramics used to prepare children's food, exposure to airborne lead due to vehicular emission, and the lead content of the dirt from the children's hands. We conclude that the major sources of lead exposure in Mexico City could be controlled by adequate public health programs to reinforce the use of unleaded gasoline and to encourage production and use of unleaded cookware instead of lead-glazed ceramics.

Adult↗
PubMed1995

Visual evoked potentials generator model derived from different spatial frequency stimuli of visual field regions and magnetic resonance imaging coordinates of V1, V2, V3 areas in man.

Visual evoked potentials (VEPs) to pattern reversal vertical bar stimuli were recorded from 24 scalp derivations (including zygomatic and inion) referenced to digitally linked earlobes in 50 controls. 1, 2 and 4 cpd patterns were presented as full field (FF) stimuli, on Upper Hemifields (UHF) and Lower Hemifields (LHF), upper and lower quadrants and with the occlusion of central and peripheral UHF and LHF. VEPs to octant stimuli were also recorded with 2 cpd patterns. N1, P1 and N2 components were recorded from posterior and inion derivations with FF stimuli, from posterior derivations with LHF stimuli, only from inion leads with UHF stimuli, from derivations ipsilateral to stimuli with quadrants and octants, and consistently from midline derivations only with lower quadrants. Polarity inverted sequences (iN1-iP1-iN2) were recorded from the other scalp derivations, with similar latency and spatial frequency sensitivity as N1-P1-N2. Single Equivalent Dipole (ED) calculations were performed on N1 and P1 recorded in the different stimulus conditions. Our findings contradict previous hypotheses on VEP generators and contradict the predictions of VEPs polarity and distribution based on the "cruciform model" of VEPs generators. In order to explain the distribution of VEPs to upper and lower half fields and to quadrant and octants, we propose a model based on the position of the medial and occipito-polar surface of visual cortex in man.

Adult↗
PubMed1995

Pulmonary arteriovenous fistula ruptured to pleural cavity in pregnancy.

Congenital pulmonary arteriovenous fistula is frequently associated with hereditary haemorrhagic telangiectasia (Rendu-Osler-Weber disease). With the increased blood flow in pregnancy such fistulas enlarge, occasionally giving rise to haemothorax, which generally has a poor prognosis. A familial case is presented in which massive haemothorax required emergency thoracotomy in the 27th week of pregnancy.

Adult↗