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Biomedical subjects

A Fink

Publications and source records attributed to A Fink.

At least 19 recordsLinked to original sources
PubMed2006

[Variance of retinal vessel diameter response to flicker light. A methodical clinical study].

AIM: The study investigated the variance of the retinal vessel response to flicker light between the right and left eyes and after a short and a medium-length time interval. METHODS: The prospective study included 28 volunteers. In the first exam both eyes were examined. One eye selected randomly was measured again after 1 h and after 1 month. The diameter response of an arterial and venous vessel segment was measured continuously by a Dynamic Vessel Analyzer (DVA, IMEDOS, Jena). Each examination consisted of 50 s baseline measurement and three periods of 20-s flicker light provocation followed by 80 s observation. The mean of three provocational cycles was calculated as dynamic vessel response. RESULTS: A significant correlation of the flicker response parameters between the right and left eyes was found. Arterial and venous baseline diameter, flicker light dilation, AVDQ, and BP did not change significantly between the first and follow-up examinations. There was no correlation between changes of BP and changes of vessel diameter parameters in the follow-up exams. CONCLUSION: Flicker-evoked dilation of retinal arterioles measured by the DVA is characterized under similar conditions by small variance after short and medium-length time periods. Therefore, this parameter is suitable as a functional parameter of the regulation ability of retinal arteries.

Anatomy, Cross-Sectional↗
PubMed2006

[Therapeutic penetrating keratoplasty for microbial keratitis].

BACKGROUND: Microbial keratitis is a potentially sight threatening disease. Most cases respond well to antimicrobial therapy. However, in cases that progress despite intensive medical therapy, an urgent therapeutic penetrating keratoplasty (TPKP) is required. AIM: To evaluate the indications and results of TPKP in Israel. METHODS: A retrospective study reviewed the TPKP performed at the Goldschleger Eye Institute, Sheba Medical Center, between 1990-2003. The study included 18 cases of at least one-year follow-up. RESULTS: The indications for TPKP included severe infectious keratitis unresponsive to medical treatment in 33% of the patients and severe corneal destruction in 66% of them. The infectious keratitis was diagnosed as bacterial keratitis in 44% of the patients, unidentified pathogen in 39%, mycotic in 11% and acanthamoeba in 6% of the patients. Risk factors in the patients with microbial keratitis requiring TPKP included: previous ocular disease in 39%, previous ocular surgery in 66%, systemic disorders in 28% and ocular risk factors in 28% patients. TPKP was successful in bacterial and acanthamoeba keratitis as far as the transparency of the graft and elimination of the infection and improvement of visual acuity. However, TPKP failed in mycotic and unidentified keratitis. The risk factors for failure included: previous ocular disease or surgeries, systemic disorders or large corneal grafts. CONCLUSIONS: Therapeutic penetrating keratoplasty is an important and effective therapeutic tool for intractable bacterial and acanthamoeba keratitis. Prognostic factors for graft success include lack of ocular disease or previous surgeries, lack of systemic disorders or small corneal graft size.

Adolescent↗
PubMed2005

Direct observation of electron dynamics in the attosecond domain.

Dynamical processes are commonly investigated using laser pump-probe experiments, with a pump pulse exciting the system of interest and a second probe pulse tracking its temporal evolution as a function of the delay between the pulses. Because the time resolution attainable in such experiments depends on the temporal definition of the laser pulses, pulse compression to 200 attoseconds (1 as = 10(-18) s) is a promising recent development. These ultrafast pulses have been fully characterized, and used to directly measure light waves and electronic relaxation in free atoms. But attosecond pulses can only be realized in the extreme ultraviolet and X-ray regime; in contrast, the optical laser pulses typically used for experiments on complex systems last several femtoseconds (1 fs = 10(-15) s). Here we monitor the dynamics of ultrafast electron transfer--a process important in photo- and electrochemistry and used in solid-state solar cells, molecular electronics and single-electron devices--on attosecond timescales using core-hole spectroscopy. We push the method, which uses the lifetime of a core electron hole as an internal reference clock for following dynamic processes, into the attosecond regime by focusing on short-lived holes with initial and final states in the same electronic shell. This allows us to show that electron transfer from an adsorbed sulphur atom to a ruthenium surface proceeds in about 320 as.

Journal Article↗
PubMed2005

EEG alpha band dissociation with increasing task demands.

In assuming functional differences between different EEG alpha frequency bands, recent studies emphasize the importance of using narrow (8-10 Hz or 10-12 Hz) instead of broad alpha frequency ranges (8-12 Hz). Due to individual differences in alpha activity, it has also been suggested to adjust alpha frequency bands individually for each participant. The present paper highlights the dissociating role of different task demands on the extent of event-related desynchronization (ERD) in different alpha frequency bands. In analyzing the data of four large-scale EEG studies (with sample sizes of 51, 58, 55, and 66, respectively) employing a wide range of cognitive tasks, we found evidence that the correlations between lower and upper alpha band ERD systematically decline as task demands increase.

Adult↗
PubMed2004

Extraversion and cortical activation during memory performance.

In this study we analyzed the influence of the personality dimension extraversion-introversion (E) on the level and topographical distribution of cortical activation. In 62 participants (32 introverts and 30 extraverts), we measured the extent of Event-Related Desynchronization (ERD) in the EEG during performance of a short-term memory (i.e., temporary maintenance of information) and a more complex working memory task (i.e., temporary maintenance and active manipulation of information). The results indicate that during performance of both tasks, introverts display a larger amount of ERD than extraverted individuals. Moreover, the present E effects largely match previous studies as to the restriction of these effects to lower EEG frequency ranges (approx. 4-8 Hz). Topographical analyses show that the E effects are primarily present over (right-hemispheric) frontal and parietal regions of the cerebral cortex.

Adult↗
PubMed2004

Intelligence and working memory systems: evidence of neural efficiency in alpha band ERD.

Starting from the well-established finding that brighter individuals display a more efficient brain function when performing cognitive tasks (i.e., neural efficiency), we investigated the relationship between intelligence and cortical activation in the context of working memory (WM) tasks. Fifty-five male (n=28) and female (n=27) participants worked on (1) a classical forward digit span task demanding only short-term memory (STM), (2) an attention-switching task drawing on the central executive (CE) of WM and (3) a WM task involving both STM storage and CE processes. During performance of these three types of tasks, cortical activation was quantified by the extent of Event-Related Desynchronization (ERD) in the alpha band of the human EEG. Correlational analyses revealed associations between the amount of ERD in the upper alpha band and intelligence in several brain regions. In all tasks, the males were more likely to display the negative intelligence-cortical activation relationship. Furthermore, stronger associations between ERD and intelligence were found for fluid rather than crystallized intelligence. Analyses also point to topographical differences in neural efficiency depending on sex, task type and the associated cognitive subsystems engaged during task performance.

Adolescent↗
PubMed2004

Postnatal shifts of interneuron position in the neocortex of normal and reeler mice: evidence for inward radial migration.

During development, interneurons migrate to precise positions in the cortex by tangential and radial migration. The objectives of this study were to characterize the net radial migrations of interneurons during the first postnatal week, and to investigate the role of reelin signaling in regulating those migrations. To observe radial migrations, we compared the laminar positions of interneurons (immunoreactive for GABA or Dlx) in mouse neocortex on postnatal days (P) 0.5 and P7.5. In addition, we used bromodeoxyuridine birthdating to reveal the migrations of different interneuron cohorts. To study the effects of reelin deficiency, experiments were performed in reeler mutant mice. In normal P0.5 cortex, interneurons were most abundant in the marginal zone and layer 5. By P7.5, interneurons were least abundant in the marginal zone, and were distributed more evenly in the cortical plate. This change was attributed mainly to inward migration of middle- to late-born interneurons (produced on embryonic days (E) 13.5 to E16.5) from the marginal zone to layers 2-5. During the same interval, late-born projection neurons (non-immunoreactive for GABA or Dlx) migrated mainly outward, from the intermediate zone to upper cortical layers. In reeler cortex, middle- and late-born interneurons migrated from the superplate on P0.5, to the deep cortical plate on P7.5. Late-born projection neurons in reeler migrated in the opposite direction, from the intermediate zone to the deep cortical plate. We conclude that many middle- and late-born interneurons migrate radially inward, from the marginal zone (or superplate) to the cortical plate, during the first postnatal week in normal and reeler mice. We propose that within the cortical plate, interneuron laminar positions may be determined in part by interactions with projection neurons born on the same day in neurogenesis.

Animals↗
PubMed2003

Sensitivity of human EEG alpha band desynchronization to different working memory components and increasing levels of memory load.

Event-related alpha band desynchronization is frequently used to analyze spatiotemporal cortical activation patterns during the performance of cognitive tasks. In the present paper the sensitivity of alpha band desynchronization to increasing levels of cognitive load and to different cognitive working memory components is investigated. A 27-channel electroencephalogram of 62 participants while solving (a) a short-term memory and (b) a working memory task (dual task), each with five levels of memory load, was analyzed. We found (a) a linearly increasing desynchronization in the upper alpha band with ascending cognitive load, and (b) evidence of the involvement of distinguishable cognitive components (storage and controlled attention) in the memory tasks.

Alpha Rhythm↗
PubMed2001

Assessing use of primary health care services by very low-income adults in a managed care program.

OBJECTIVE: To assess the effect of providing free health care services to low-income adults. METHODS: We measured access to primary care services by enrollees with 4 chronic medical conditions in the General Relief Health Care Program (GRHCP), a program designed for adults receiving General Relief (GR). Implemented by the Los Angeles County Health Department in October 1995, the GRHCP is composed of private and public health care facilities. As adults registered for GR, they were asked to complete a baseline health survey, were enrolled in the GRHCP, and assigned a health care provider. A total of 8520 surveys were completed between September and November 1996 (98% response rate). The analyses of this article are limited to individuals (N = 2164) who reported a history of hypertension, diabetes mellitus, a nonresolving cough, or substance dependence. We reviewed medical records to determine whether new GR recipients had visited their designated GRHCP provider within 4 months of enrollment and used multivariate logistic regression to assess the effect of individual patient factors on the use of free health care. RESULTS: A total of 17% of individuals visited their assigned GRHCP provider within 4 months of enrollment. In multivariate analysis, patients were more likely to have made a visit if they were younger than 50 years, were female, were Asian/Pacific Islander, reported needing to see a physician, or had seen a physician within 12 months. CONCLUSIONS: It is not sufficient to merely supply the name and address of a health care provider to this population. More aggressive efforts should be attempted to increase utilization of services for patients with medical conditions responsive to ambulatory care.

Female↗
PubMed2001

Informing older adults about non-hazardous, hazardous, and harmful alcohol use.

Low levels of alcohol may be hazardous in the elderly, but available education focuses on younger, abusive, and dependent drinkers. A total of 209 older persons participated in various components of the development and evaluation of 'A Toast To Health In Later Life!' health promotion materials for the elderly. Patient focus groups, physicians, educators, and alcohol-use researchers contributed to all materials and measures. An education model for older adults guided the instructional format. Knowledge and self-efficacy scores increased significantly from pre- to post-test. Over 45% of persons in selected senior centers reviewed the materials without prompting by the study team. Older adults are willing to read extensively about the relationships among drinking, health, and medication use. Patient educators should include consumers in the design of health promotion materials and measures. Practitioners who rely on written educational materials for patient education and counseling should be provided with evidence of appropriateness, effectiveness, and feasibility.

Aged↗
PubMed2001

Using data to enhance the expert panel process. Rating indications of alcohol-related problems in older adults.

OBJECTIVE: To enhance the validity of a well-known expert panel process, we used data from patient surveys to identify and correct rating errors. METHODS: We used the two-round RAND/UCLA panel method to rate indications of harmful (presence of problems), hazardous (at risk for problems), and nonhazardous (no known risks) drinking in older adults. Results from the panel provided guidelines for classifying older individuals as harmful, hazardous, or nonhazardous drinkers, using a survey. The classifications yielded unexpectedly high numbers of harmful and hazardous drinkers. We hypothesized possible misclassifications of drinking risks and used the survey data to identify indications that may have led to invalid ratings. We modified problematic indications and asked three clinician panelists to evaluate the clinical usefulness of the modifications in a third panel round. We revised the indications based on panelist response and reexamined drinking classifications. RESULTS: Using the original indications, 48% of drinkers in the sample were classified as harmful, 31% as hazardous, and 21% as nonhazardous. A review of the indications revealed framing bias in the original rating task and vague definitions of certain symptoms and conditions. The modified indications resulted in classifications of 22% harmful, 47% hazardous, and 31% nonhazardous drinkers. CONCLUSIONS: Analysis of survey data led to identification and correction of specific errors occurring during the panel-rating process. The validity of the RAND/UCLA method can be enhanced using data-driven modifications.

Aged↗
PubMed2001

Towards functional proteomics of membrane protein complexes: analysis of thylakoid membranes from Chlamydomonas reinhardtii.

Functional proteomics of membrane proteins is an important tool for the understanding of protein networks in biological membranes but structural studies on this part of the proteome are limited. In this study we undertook such an approach to analyse photosynthetic thylakoid membranes isolated from wild-type and mutant strains of Chlamydomonas reinhardtii. Thylakoid membrane proteins were separated by high-resolution two-dimensional gel electrophoresis (2-DE) and analysed by immuno-blotting and mass spectrometry for the presence of membrane-spanning proteins. Our data show that light-harvesting complex proteins (LHCP), that cross the membrane with three transmembrane domains, can be separated using this method. We have identified more than 30 different LHCP spots on our gels. Mass spectrometric analysis of 2-DE separated Lhcb1 indicates that this major LHCII protein can associate with the thylakoid membrane with part of its putative transit sequence. Separation of isolated photosystem I (PSI) complexes by 2-DE revealed the presence of 18 LHCI protein spots. The use of two peptide-specific antibodies directed against LHCI subunits supports the interpretation that some of these spots represent products arising from differential processing and post-translational modifications. In addition our data indicate that the reaction centre subunit of PSI, PsaA, that possesses 11 transmembrane domains, can be separated by 2-DE. Comparison between 2-DE maps from thylakoid membrane proteins isolated from a PSI-deficient (Deltaycf4) and a crd1 mutant, which is conditionally reduced in PSI and LHCI under copper-deficiency, showed the presence of most of the LHCI spots in the former but their absence in the latter. Our data demonstrate that (i) hydrophobic membrane proteins like the LHCPs can be faithfully separated by 2-DE, and (ii) that high-resolution 2-DE facilitates the comparative analysis of membrane protein complexes in wild-type and mutants cells.

Amino Acid Sequence↗
PubMed2001

Comparison of surgical outcomes between teaching and nonteaching hospitals in the Department of Veterans Affairs.

OBJECTIVE: To determine whether the investment in postgraduate education and training places patients at risk for worse outcomes and higher costs than if medical and surgical care was delivered in nonteaching settings. SUMMARY BACKGROUND DATA: The Veterans Health Administration (VA) plays a major role in the training of medical students, residents, and fellows. METHODS: The database of the VA National Surgical Quality Improvement Program was analyzed for all major noncardiac operations performed during fiscal years 1997, 1998, and 1999. Teaching status of a hospital was determined on the basis of a background and structure questionnaire that was independently verified by a research fellow. Stepwise logistic regression was used to construct separate models predictive of 30-day mortality and morbidity for each of seven surgical specialties and eight operations. Based on these models, a severity index for each patient was calculated. Hierarchical logistic regression models were then created to examine the relationship between teaching versus nonteaching hospitals and 30-day postoperative mortality and morbidity, after adjusting for patient severity. RESULTS: Teaching hospitals performed 81% of the total surgical workload and 90% of the major surgery workload. In most specialties in teaching hospitals, the residents were the primary surgeons in more than 90% of the operations. Compared with nonteaching hospitals, the patient populations in teaching hospitals had a higher prevalence of risk factors, underwent more complex operations, and had longer operation times. Risk-adjusted mortality rates were not different between the teaching and nonteaching hospitals in the specialties and operations studied. The unadjusted complication rate was higher in teaching hospitals in six of seven specialties and four of eight operations. Risk adjustment did not eliminate completely these differences, probably reflecting the relatively poor predictive validity of some of the risk adjustment models for morbidity. Length of stay after major operations was not consistently different between teaching and nonteaching hospitals. CONCLUSION: Compared with nonteaching hospitals, teaching hospitals in the VA perform the majority of complex and high-risk major procedures, with comparable risk-adjusted 30-day mortality rates. Risk-adjusted 30-day morbidity rates in teaching hospitals are higher in some specialties and operations than in nonteaching hospitals. Although this may reflect the weak predictive validity of some of the risk adjustment models for morbidity, it may also represent suboptimal processes and structures of care that are unique to teaching hospitals. Despite good quality of care in teaching hospitals, as evidenced by the 30-day mortality data, efforts should be made to examine further the structures and processes of surgical care prevailing in these hospitals.

Education, Medical, Graduate↗
PubMed2001

Problematic substance use, depressive symptoms, and gender in primary care.

This study determined the frequency of problematic substance use and of counseling about drug and alcohol use among 867 women and 320 men who reported symptoms of depression in managed primary care clinics. Seventy-two (8.3 percent) of the women and 61 (19 percent) of the men reported hazardous drinking; 228 (26.3 percent) of the women and 94 (29.4 percent) of the men reported problematic drug use, including use of illicit drugs and misuse of prescription drugs. Only 17 (13.9 percent) of the patients who reported hazardous drinking and 18 (6.6 percent) of those who reported problematic drug use received counseling about drug or alcohol use during their last primary care visit. Men were significantly more likely than women to have received counseling about drug or alcohol use from their primary care practitioner.

Adolescent↗
PubMed2000

Family planning clinic patients: their usual health care providers, insurance status, and implications for managed care.

PURPOSE: To understand the extent to which family planning clinic patients have health insurance or access to other health care providers, as well as their preferences for clinic versus private reproductive medical care. METHOD: An anonymous self-report questionnaire was administered at three Planned Parenthood clinics in Los Angeles County to 780 female patients aged 12-49 years. Dependent variables included insurance status, usual source of care, and a battery of questions regarding the importance of confidentiality. RESULTS: A total of 356 adolescents (aged 12-19 years) and 424 adults (aged 20-49 years) completed the survey in 1994. Fifty-nine percent of adolescents and 53% of adults had a usual source of care other than the clinic. The majority of each group reported some degree of continuity of care in their usual provider setting. Nearly half (49%) of all adolescents had health insurance compared with 27% of adults. Adolescents cited not wanting to involve family members as the primary reason for not using their usual providers, whereas adults were more likely to cite being uninsured. The majority of both adult and adolescent patients indicate they would prefer the clinic over private health care if guaranteed health care that was free, confidential, or both. CONCLUSION: Despite many patients' having health insurance and other sources of health care, family planning clinics were primarily chosen because of cost and confidentiality. Their reasons for preferring clinics may continue despite changes in access to insurance or efforts to incorporate similar reproductive services into mainstream health care provider systems. Making public or private health care funds available to family planning clinics through contracts or other mechanisms may facilitate patients' access to essential services and reduce potential service duplication.

Adolescent↗