PubMed Health⌕ Search

Biomedical subjects

M Eichler

Publications and source records attributed to M Eichler.

16 recordsLinked to original sources
PubMed2001

Measurement of parenting self-efficacy and outcome expectancy related to discussions about sex.

The purpose of this study was to evaluate the psychometric properties of two scales--one to measure the self-efficacy of parents to discuss sexual health issues with their adolescents and the other to measure parents' outcome expectancy associated with such discussions. Understanding how parents feel about their confidence in talking with their children about important sexual health issues and the outcomes they expect as a result of such discussions can be useful in guiding both the development and refinement of educational programs to promote parent-child discussions. The responses of 491 mothers who participated in an HIV prevention intervention with their adolescents were used for the present analysis. Mothers ranged in age from 25 to 68 years with a mean of 37.9 years (SD = 6.9). Of mother participants, 33% were married, 96.7% were African American, and 89.2% had completed high school. Their adolescents ranged in age from 11 to 14 years, and 61.5% were male. Assessment of reliability for both scales showed that internal consistency reliability was acceptable for the total scales as well as three of the five subscales. With the exception of one item on the outcome expectancy scale, the inter-item correlations, the mean inter-item correlations, and the item-to-total correlations meet the standard criteria for scale development for both scales. Factor analysis was used to identify the underlying structure of the scales, and hypothesis testing was used to assess construct validity. The results of these analyses provide support for the construct validity of the scales.

Adolescent↗
PubMed2000

A library of atmospheric pressure ionization daughter ion mass spectra based on wideband excitation in an ion trap mass spectrometer.

A searchable library of MS/MS spectra obtained using a quadrupole ion trap mass spectrometer and electrospray or atmospheric pressure chemical ionization is presented. The application of wideband excitation (activation) and normalized collision energy leads to highly reproducible mass spectra which are searched using the NIST algorithm. Flow injection and LC/MS/MS applications of this powerful technique in the biomedical (diastereoisomeric steroids, morphine glucuronides, isovalerylcarnitine) and environmental (pirimicarb and desmethyl-pirimicarb) areas are described.

Algorithms↗
PubMed2000

Can vortices in the flow across mechanical heart valves contribute to cavitation?

Cavitation in mechanical heart valves is traditionally attributed to the hammer effect and to squeeze and clearance flow occurring at the moment of valve closure. In the present study, an additional factor is considered--the contribution of vortex flow. Using a computational fluid dynamics analysis of a 2D model of a tilting disk mitral valve, we demonstrate that vortices may form in the vicinity of the inflow side of the valve. These vortices roll up from shear layers emanating from the valve tips during regurgitation. A significant decrease in the pressure at the centre of the vortices is found. The contribution of the vortex to the total pressure drop at the instant of closure is of the order of 70 mmHg. Adding this figure to the other pressure drop sources that reach 670 mmHg, it might be that this is the deciding factor that causes the drop in blood pressure below vapour pressure. The total pressure drop near the upper tip (750 mmHg) is larger than near the lower tip (670 mmHg), indicating a preferential location for cavitation inception, in agreement with existing experimental findings.

Blood Flow Velocity↗
PubMed2000

Origin and appearance of HITS induced by prosthetic heart valves: an in vitro study.

Patients with mechanical heart valve prostheses show significantly enhanced numbers of HITS detected by transcranial Doppler ultrasound. In order to assess the origin of HITS formation, an in vitro study was set out to quantify valve induced microemboli for mechanical and bioprosthetic valves under various circulatory conditions by means of Ultrasound-Doppler-Sonography. At the same time the influence of CO2 partial pressure on HITS rate vas investigated. It can be summarised that for mechanical heart valve prostheses a strong correlation exists between left ventricular dp/dtmax and the detected HITS rates. It was also demonstrated that a bioprosthesis generates significantly less HITS than a mechanical valve. The origin of HITS is gaseous since the tests were carried out using a cell-free filtered water-glycerol test fluid. The HITS rate could be increased by increasing the amount of dissolved gas within the test fluid. The results support the hypothesis that cavitation is the key factor in the appearance of gaseous microemboli at heart valve prostheses.

Heart Valve Prosthesis↗
PubMed1997

Identification of synaptic connections in neural ensembles by graphical models.

A method for the identification of direct synaptic connections in a larger neural net is presented. It is based on a conditional correlation graph for multivariate point processes. The connections are identified via the partial spectral coherence of two neurons, given all others. It is shown how these coherences can be calculated by inversion of the spectral density matrix. In simulations with GENESIS, we discuss the relevance of the method for identifying different neural ensembles including an excitatory feedback loop and networks with lateral inhibitions.

Computer Graphics↗
PubMed1996

Recognition of laparoscopic bile duct injuries by intraoperative ultrasonography.

BACKGROUND: The purpose of this study was to investigate the possibility of detecting bile duct injuries using laparoscopic intraoperative ultrasound (LIOU). METHODS: Fifty bile duct injuries were created using laparoscopic techniques in ten farmer pigs. The lesions created were: (1) partial occlusion, (2) complete occlusion (1 clip), (3) complete occlusion (2 clips), (4) transection between clips, (5) excision between clips. RESULTS: All injuries were easily visualized using LIOU. The relation of clips impinging upon or occluding the bile duct was readily visualized on LIOU in all cases. In some cases it was difficult to distinguish between partial and complete occlusion. It was also difficult to distinguish between transection and excision due to retraction of the severed bile duct. CONCLUSIONS: In cases of iatrogenic occlusion of the bile duct involving hemoclips (including transection or excision between clips), LIOU is a potentially useful modality that may allow earlier recognition and repair. Further studies are needed to evaluate the efficacy of LIOU in detection of bile duct injuries that do not involve hemoclips.

Animals↗
PubMed1996

In vitro testing of heart valve wear outside of the manufacturers laboratory--requirements and controversies.

BACKGROUND AND AIM OF THE STUDY: Currently, various national and international Standards regulate in vitro and in vivo testing as well as the clinical evaluation of heart valve prostheses. This study concentrates on a single aspect of these protocols: accelerated wear and fatigue testing. METHODS: The differences in the above Standards were appraised and an experimental study was designed to assess the validity of Standard testing conditions with respect to in vivo relevance. An instrumented BSCC tilting disc valve was tested in two different types of fatigue testers and in a separate study in a sheep model. RESULTS: By comparing the obtained results it could be clearly demonstrated that under the current Standard conditions (ISO, CEN, FDA) actual in vivo impact loading cannot be reproduced. Also, the two compared test devices, though operating under the same Standard conditions, generated totally different loading conditions on the test valve. CONCLUSIONS: Based on these findings it is suggested that the actual loading conditions of each valve type should be measured either in vivo in animal models or within a circulatory mock loop which provides physiologic loading conditions, and the test conditions for accelerated wear and fatigue testing should be modified accordingly. Cavitation effects which can be assumed to be associated with high frequency wear testing is another important issue which has to be addressed in future amendments to the Test Standards.

Animals↗
PubMed1995

The effect of left ventricular dP/dt on the in vitro dynamics of the Björk-Shiley Convexo-Concave mitral valve.

Left ventricular (LV) dP/dt is considered an important hemodynamic factor influencing the dynamics of mechanical heart valve prostheses. LV dP/dt is dependent on patient factors including age, cardiac activity, health, and medication. The objective of this study was to determine the effect of LV dP/dt on the closing dynamics of mechanical heart valve prostheses in the mitral position. Eight instrumented 29 mm Björk-Shiley Convexo-Concave (BSCC) heart valves were tested in the pulse duplicator of the Helmholtz Institute. The valves had miniature strain gages mounted at the base of the outlet strut to measure impact loads at closure. Closing velocities were measured with a "light gate" device which was triggered by the closing leaflet. Physiologic pressure and flow waveforms were generated by a computer-controlled hydraulic drive unit. LV dP/dt was varied from 500 to 4000 mmHg/s simulating a wide range of physiologic conditions. It was found that the closing velocity was almost linearly related to LV dP/dt. At 4000 mmHg/s, closing velocities ranged from 1.5 to 2.0 m/s. Impact loads increased monotonically with LV dP/dt and closing velocity. In some valves, impact loads reached 2800 g at LV dP/dt of 4000 mmHg/s, and closing velocities of 2.0 m/s.

Animals↗
PubMed1989

[What is the contribution of yeast genetics to tumor biology and tumor diagnosis?].

This short review article discusses methods and results of oncogene research in yeast. Current knowledge of the sequence, expression and biological function of ras-homologous genes of the yeast Saccharomyces cerevisiae is presented, as well as the implications of these findings for oncogene research in mammals. We review recent examples of highly conserved eukaryotic genes involved in growth control and mitosis control, including recent work from our own laboratories.

Cloning, Molecular↗
PubMed1989

AIDS cases with no identified risk: artifact or reality? The Connecticut example.

Connecticut's 66 AIDS cases initially reported with no identified risks (NIRS) were reviewed and intensively investigated. Investigation resulted in reclassification of 45 cases (68.2%) to categories of known risk; one case (1.5%) was misdiagnosed as AIDS. Twenty cases (30.3%) remain NIRS because no risk could be established at this time. Evidence that NIRS represent reporting artifact, rather than unknown or new modes of transmission, was found. (1) NIRS are cases for which information on sexual behavior is highly sensitive or difficult to obtain. After investigation, 72% of reclassified Connecticut NIRS were determined to have risks related to sexual transmission. (2) The percentage of NIRS fluctuates according to reporting source and method of investigation. Within Connecticut, major reporting sources vary from a high of 15% to a low of 0% NIRS among their cases. The most effective method for establishing risks was to obtain information from reporting sources.

Acquired Immunodeficiency Syndrome↗
PubMed1988

AIDS in Connecticut.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1976

Volunteers as relationship therapists for institutionalized geriatric patients.

In a three year demonstration project we trained non-professional volunteers to carry out relationship therapy with emotionally disturbed geriatric patients at Levindale, a long-term-care old age home and chronic disease hospital. This was part of an overal program to create a therapeutic milieu in the institution which would oppose the disculturation, stripping processes. The selection and training program are described. The results with the volunteer counselors and the impact of their work on the structure and functioning of all levels of the institutional life are detailed. Recommendations are made for carrying out such a program in other long-term-care settings.

Administrative Personnel↗
PubMedDate not supplied

A general strategy for site-specific double labeling of globular proteins for kinetic FRET studies.

Site-directed mutagenesis provides a straightforward means of creating specific targets for chemical modifications of proteins. This capability enhanced the applications of spectroscopic methods adapted for addressing specific structural questions such as the characterization of partially folded and transient intermediate structures of globular proteins. Some applications such as the steady state or time-resolved fluorescence resonance energy transfer (FRET) detection of the kinetics of protein folding require relatively large quantities (approximately 10-100 mg) of site-specific doubly labeled protein samples. Engineered cysteine residues are common targets for labeling of proteins. The challenge here is to develop methods for selective modification of one of two reactive sulfhydryl groups in a protein molecule. A general systematic procedure for selective labeling of each of two cysteine residues in a protein molecule was developed, using Escherichia coli adenylate kinase (AKe) as a model protein. Potential sites for insertion of cysteine residues were selected by examination of the crystal structure of the protein. A series of single-cysteine mutants was prepared, and the rates of the reaction of each engineered cysteine residue with a reference reagent [5,5'-dithiobis(2-nitrobenzoic acid) (DTNB)] were determined. Two-cysteine mutants were prepared by selection of pairs of sites for which the ratio of this reaction rate constant was high (>80). The conditions for the selective labeling reaction were optimized. In a first cycle of labeling, the more reactive cysteine residue was labeled with a fluorescent probe (donor). The second probe was attached to the less reactive site under unfolding conditions in the second cycle of labeling. The doubly and singly labeled mutants retained full enzymatic activity and the capacity for a reversible folding-unfolding transition. High yields (70-90%) of the preparation of the pure, site-specific doubly labeled AK mutant were obtained. The procedure described herein is a general outline of procedures, which can meet the double challenge of both site specificity and large-scale preparation of doubly labeled proteins.

Adenylate Kinase↗