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Biomedical subjects

B Herman

Publications and source records attributed to B Herman.

At least 19 recordsLinked to original sources
PubMed2003

Quantitative imaging of protein-protein interactions by multiphoton fluorescence lifetime imaging microscopy using a streak camera.

Fluorescence lifetime imaging microscopy (FLIM) using multiphoton excitation techniques is now finding an important place in quantitative imaging of protein-protein interactions and intracellular physiology. Recent developments in multiphoton FLIM methods are reviewed and a novel multiphoton FLIM system using a streak camera is described. An example of a typical application of the system is provided in which the fluorescence resonance energy transfer between a donor-acceptor pair of fluorescent proteins within a cellular specimen is measured.

Animals↗
PubMed2001

An overview of videostreaming on the Internet and its application to surgical education.

The Information Age has endowed mankind with a wealth of new technologies. Applications of these technologies are being developed to facilitate content exchange between individuals and institutions. Internet streaming is an exciting new technology that allows multimedia content to be stored and sent over the Internet, and medical educators are challenged to harness the potential of streaming for educational enhancement. This article helps to define streaming, examining its potential for surgical education.

Computer-Assisted Instruction↗
PubMed2001

Telementoring and teleproctoring.

Telemedicine has previously been defined as "live two-way interactive video communication between a physician and a patient and/or another physician, where all participants are able to see and hear one another much like a face to face encounter." This concept has gained recent notoriety because of the great advances in telecommunications and the potential future increased cost-effectiveness associated with its utilization. We have developed a telementoring deployment protocol that can be effectively used to introduce a student to telementoring processes. The strict protocol uses military commands to facilitate smooth information transfer. The use of a concept called tactical information deployment provides the surgeon with rapid access to reference information in the operating suite. Multimedia interactive CD-ROMs, with digitized movie clips, illustrations, sound bits, and the latest academic review of the literature arm the surgeon with a database that establishes an unprecedented clinical adaptive capability (CAC). The availability of this information is invaluable to surgeons in their initial advanced laparoscopic procedural efforts. Telementoring simulator opportunities are included to acclimate the participant to the process. If the process seems comprehensive, it is meant to be. This is a high-risk situation, and a patient's welfare is on the line. If this concept is to reach its maximal healthcare delivery potential, responsible and academically credible training programs should be established with directional guidelines.

Computer-Assisted Instruction↗
PubMed2001

Patterns of resource allocation are reliable among younger and older readers.

Younger and older adults read short expository passages across 2 times of measurement for subsequent comprehension or recall. Regression analysis was used to decompose word-by-word reading times into resources allocated to word- and textbase-level processes. Readers were more sensitive to these demands when reading for recall than when reading for comprehension. Patterns of resource allocation showed good test-retest reliabilities and were predictive of memory performance. Within age group, resource allocation parameters were not systematically correlated with other individual-difference measures, suggesting that strategies of on-line resource allocation may be a unique source of individual differences in determining comprehension of and memory for text. Age differences in allocation patterns appeared to reflect general slowing among the older adults. Because older adults showed equivalent memory performance to that of younger readers, the reading time data may represent the on-line resource allocation needed for comparable outcomes among older and younger readers.

Adolescent↗
PubMed2001

Right ventricular response to high-dose almitrine infusion in patients with severe hypoxemia related to acute respiratory distress syndrome.

OBJECTIVE: To evaluate the effects of high-dose almitrine infusion on gas exchange and right ventricular function in patients with severe hypoxemia related to acute respiratory distress syndrome (ARDS). DESIGN: Prospective study. SETTING: Medicosurgical intensive care department (ten beds). PATIENTS: Nine patients with ARDS and severe hypoxemia (PaO2/FIO2 ratio, <150 torr [20 kPa]). INTERVENTION: High-dose almitrine infusion (16 microg/kg/min for 30 mins). MEASUREMENTS AND MAIN RESULTS: Gas exchange and hemodynamic parameters were recorded before and after almitrine infusion. Right ventricular function was evaluated by using a fast response thermistor pulmonary artery catheter that allowed measurement of right ventricular ejection fraction and calculation of right ventricular end-diastolic and end-systolic volumes. Almitrine did not significantly alter arterial oxygenation and intrapulmonary shunt. Almitrine increased mean pulmonary arterial pressure (MPAP) from 31 +/- 4 to 33 +/- 4 mm Hg (p < .05), pulmonary vascular resistance index from 353 +/- 63 to 397 +/- 100 dyne x sec/ cm5 x m2 (p < .05), and right ventricular end-systolic volume index from 71 +/- 22 to 77 +/- 21 mL/m2 (p < .05); almitrine decreased right ventricular ejection fraction from 36% +/- 7% to 34% +/- 8% (p < .05). Stroke volume index and cardiac index did not change. The almitrine-induced changes in right ventricular ejection fraction were closely correlated with the baseline MPAP (r2 = .71, p < .01). CONCLUSION: In patients with severe hypoxemia related to ARDS, high-dose almitrine infusion did not improve arterial oxygenation and impaired the loading conditions of the right ventricle. The decrease in right ventricular ejection fraction induced by almitrine was correlated with the baseline MPAP. Thus, high-dose almitrine infusion may be harmful in ARDS patients with severe hypoxemia and pulmonary hypertension.

Adult↗
PubMed2001

Measurement of mitochondrial pH in situ.

In this article, we describe the advantages and disadvantages of procedures for monitoring mitochondrial pH in situ using optical microscopic techniques. The first method employs the combination of the fluorescent pH-sensitive indicator carboxy-SNARF and laser scanning confocal microscopy. Manipulation of the loading and post-loading conditions enables relatively specific accumulation of carboxy-SNARF into mitochondria. With the use of a mitochondrial-specific marker, mitochondrial pH can be accurately monitored. More recently, mitochondrial-targeted, pH-sensitive probes have been used to monitor mitochondrial pH. In particular, mitochondrial targeting of the yellow fluorescent protein (YFP) mutant of green fluorescent protein (GFP) combines the advantages of specific mitochondrial localization, high-fluorophore quantum yield, and extinction coefficient with an appropriate pKa for measuring mitochondrial pH. The use of dual-excitation ratiometry with mitochondrially targeted YFP increases the dynamic range of mitochondrial pH measurements and corrects for differences in the amount of expression of mitochondrially targeted YFP at the level of individual mitochondria.

Bacterial Proteins↗
PubMed2000

Effectiveness of a CD-ROM multimedia tutorial in transferring cognitive knowledge essential for laparoscopic skill training.

BACKGROUND: Computer-assisted instruction (CAI) can benefit surgical education by improving efficiency, effectiveness, standardization, and access. This study compares knowledge gains for laparoscopic skill acquisition following a standardized tutorial delivered via CD-ROM versus live instructor. METHODS: A standardized tutorial was written and subsequently converted to multimedia CD-ROM format by its author (JR). During a laparoscopic development course, experienced US-trained surgeons (n = 52) participated in the tutorial delivered live by the author. The CD-ROM tutorial replaced the instructor for the following groups: (1) experienced US-trained surgeons (n = 27); (2) US-trained surgical residents (n = 59); and (3) Greek surgeons (n = 63). A 51-item knowledge test was administered before and after tutorial instruction. RESULTS: The mean increase in scores between pretest and posttest was significant (P <0.01) and of similar magnitude in each group, with nonsignificant posttest mean differences among US-trained groups. CONCLUSIONS: The CD-ROM tutorial effectively transfers cognitive information necessary for skill development. Distance learning modes of this tutorial program may be feasible.

CD-ROM↗
PubMed2000

Feasibility of mitral flow assessment by echo-contrast ultrasound, part I: determination of the properties of echo-contrast agents.

Data on the ultrasonic properties of commercially available contrast agents are limited by being instrument-dependent, especially with regard to their backscattering properties. The present work describes methods of measurements that provide instrument-independent estimations of a contrast agent's attenuation coefficient and integrated backscatter index and provide them as functions of its concentration. The two studied commercially available contrast agents were Albunex and Levovist SHU 508-A, both representative of agents in common use for echocardiography. The attenuation coefficients and integrated backscatter indices of both agents were found to be a linear function of their concentrations. Proportionality coefficients +/- their standard deviations are provided. Actually, square root values of the averaged backscatter indices normalized with respect to the rms of the reference signal were determined. The coefficients of proportionality were found to be: C(A) = 3.11+/-0.1813 dB/mm; C(L) = 0.07+/-0.005 dB/mm for attenuation coefficients of the Albunex and Levovist contrast agents, respectively, and the corresponding values for backscattering were: D(A) = 0.07+/-0.0054; D(L) = 0.02+/-0.0012. Being apparatus-independent, the findings of the study are important prerequisites for the use of these echo-contrast agents as an indicator in research for a quantitative assessment of blood flow.

Albumins↗
PubMed2000

Feasibility of mitral flow assessment by echo-contrast ultrasound, part II: experimental study on a mechanical model of the left heart.

The feasibility of assessing mitral flow by means of ultrasonic monitoring of backscattered power from an echo-contrast agent in the left atrium and left ventricle was studied. A mechanical model of the left heart was built in which two thin rubber balloons connected to each other in a feedback loop via two artificial heart valves mimicked the left atrium and left ventricle. The model was driven by compressed air. Its input and output flows were measured as the functions of a pacing rate, driving pressure and artificially introduced mitral regurgitation. These were compared with the corresponding data derived from the ultrasonic measurements that are based on the correlation between echo-contrast agent concentration in the volume of interest and the flow through it. Algorithms for quantitative estimations of forward stroke volume (cardiac output) and mitral regurgitation are given. This study shows, for the first time, both analytically and experimentally, that the pulsating modulation of contrast agent concentration vs. time curves in the ventricle and atrium volumes is closely related to the pulsating nature of the flow in the system. It also shows that the amplitude of the atrium concentration modulation is directly proportional to the maximum value of the incoming (to atrium) flow.

Albumins↗
PubMed2000

Differential sensitivity of mouse neural crest cells to ethanol-induced toxicity.

Neural crest cells (NCCs) have been identified as an important target population relative to ethanol-induced teratogenicity in both mouse and avian models. Additionally, whole embryo culture mouse models have shown strain-related differences in sensitivity to ethanol-induced damage following acute exposure during early NCC development. That differential sensitivity of NCCs may contribute to these strain differences has been unexplored. For this purpose, cultured NCCs from an inbred mouse strain (C57BL/6J; C57) that is more sensitive to ethanol-induced teratogenicity than an outbred strain (ICR) were compared. This study showed that the incidence of cell death was significantly higher for the C57 NCCs than those from the ICR strain at all ethanol concentrations tested, and as early as 12 hours after initial exposure to 100 mM ethanol. The lateral mobility of the membrane lipids was faster and the membrane GM1 content was lower in C57 cells than ICR cells both under control conditions and at all doses and times tested. Ethanol exposure resulted in significant increases in the membrane lipid lateral mobility, and decreases in the membrane GM1 content that occurred in a dose and time-dependent manner in the NCCs from both strains. A significant correlation was found between the GM1 content and lateral mobility of the membrane lipids, the lateral mobility of membrane lipids and cell viability, as well as the GM1 content and cell viability in the NCCs from both strains. These results suggest that different strain sensitivities to ethanol-induced teratogencity may lie, at least in part, in the interstrain differential response of the NCC population and that the vulnerability of the NCCs to ethanol-induced death may be related to their endogenous membrane GM1 content.

Animals↗
PubMed2000

Multicenter prospective study of ventilator-associated pneumonia during acute respiratory distress syndrome. Incidence, prognosis, and risk factors. ARDS Study Group.

We investigated the incidence, risk factors for, and outcome of ventilator-associated pneumonia (VAP) in patients with acute respiratory distress syndrome (ARDS). We compared 134 patients with ARDS with 744 patients without ARDS on mechanical ventilation. Fiberoptic bronchoscopic examination and quantitative bacterial cultures (protected brush or catheter sampling [threshold: 10(3) cfu/ml], or bronchoalveolar lavage [threshold: 10(4) cfu/ml]) were used to diagnose pneumonia. VAP occurred in 49 patients (36.5%). The incidence of pneumonia was 23% (173 of 744 patients) among patients without ARDS (p < 0.002). Nonfermenting gram-negative rods caused significantly more pneumonia in ARDS patients. Mortality rates were identical in ARDS patients with (28 of 49 patients, 57%) and without (50 of 85 patients, 59%) pulmonary infection (p = 0.8). VAP resulted in a considerable increase in attributable time on mechanical ventilation of both the overall population of ARDS patients and of survivors. Both the use of sucralfate (adjusted odds ratio [OR]: 4. 42; 95% confidence interval [CI]: 2.01 to 9.7, p = 0.0002) and the duration of exposure to sucralfate (adjusted OR: 1.206; 95% CI: 1. 095 to 1.328, p = 0.0002) were associated with an increased risk of VAP during ARDS. VAP considerably prolongs the time on mechanical ventilation without affecting survival. Patients given sucralfate may be at greater risk of developing pulmonary infection during ARDS.

Adult↗
PubMed2000

Localization of Rat Liver Group IIA Phospholipase A(2) in Secretory Pathways: Green Fluorescent Protein Approach.

Rat liver group IIA phospholipase A(2) (PLA(2), Enzyme Commission Number [E.C.] 3.1.1.4) was initially isolated from mitochondria. Since then it has been thought that it resides in mitochondria and that mitochondria are its main subcellular target. We cloned the cDNA sequence of rat group IIA PLA(2) and fused its presequence (signal peptide) to enhanced green fluorescent protein (EGFP). In baby hamster kidney (BHK) cells transiently and stably expressing the fusion protein, the fluorescence does not localize in mitochondria, but rather in the secretory pathway. These results suggest that the plasma membrane, and not mitochondria, is the primary target of rat group IIA PLA(2).

Journal Article↗
PubMed2000

Human papillomavirus type 16 E6 and HPV-16 E6/E7 sensitize human keratinocytes to apoptosis induced by chemotherapeutic agents: roles of p53 and caspase activation.

We and others have previously reported that human papillomavirus (HPV)-16 E6 protein expression sensitizes certain cell types to apoptosis. To confirm that this sensitization occurred in HPV's natural host cells, and to explore the mechanism(s) of sensitization, we infected human keratinocytes (HKCs) with retroviruses containing HPV-6 E6, HPV-16 E6, HPV-16 E7, or HPV-16 E6/E7. Apoptosis was monitored by DNA fragmentation gel analysis and direct observation of nuclei in cells stained with DAPI. Exposure of HKCs to etoposide, cisplatin, mitomycin C (MMC), atractyloside, and sodium butyrate, resulted in a time and dose-dependent induction of apoptosis. Expression of HPV-16 E6 and HPV-16 E6/E7, but not HPV-6 E6 or HPV-16 E7, enhanced the sensitivity of HKCs to cisplatin-, etoposide- and MMC-, but not atractyloside- or sodium butyrate-induced apoptosis. Expression of both HPV-16 E6 and HPV-16 E6/E7 decreased, but did not abolish, p53 protein levels relative to normal HKCs, and resulted in cytoplasmic localization of wt p53. P53 induction occurred in HPV-16 E6 and HPV-16 E6/E7 expressing cells after exposure to cisplatin or MMC, though never to levels found in normal untreated HKCs. P21 levels were decreased in HPV-16 E6 and HPV-16 E6/E7 expressing HKCs, and no induction of p21 was seen in these cells following exposure to cisplatin or MMC. Caspase-3 activity was found to be elevated in HPV-16 E6-expressing HKCs following exposure to cisplatin and MMC as documented by fluorometric and Western Blot analysis. Expression of wt CrmA or treatment of HPV-16 E6 expressing HKCs with the caspase-3 inhibitor DEVD.fmk prevented HPV-16 E6-induced sensitization in HKCs. These results suggest that HPV-16 E6 and HPV-16 E6/E7 expression sensitizes HKCs to apoptosis caused by cisplatin, etoposide and MMC, but not atractyloside or sodium butyrate. The data also suggest that wt p53 and caspase-3 activity are required for HPV-16 E6 and HPV-16 E6/E7-induced sensitization of HKCs to DNA damaging agents.

Apoptosis↗
PubMed1999

Secretory group IIA phospholipase A(2) generates anti-apoptotic survival signals in kidney fibroblasts.

Mammalian group IIA phospholipase A(2) (PLA(2)) is believed to play important roles in inflammation, cell injury, and tumor resistance. However, the cellular site of action has not been clearly defined as it has long been recognized that group IIA PLA(2) is both a secretory and mitochondrial protein. The purpose of this study was to determine the subcellular target of the group IIA PLA(2) and its role in apoptosis stimulated by growth factor withdrawal. Cloning of the rat liver group IIA PLA(2) demonstrated a typical secretory signal and no alternative splicing of the primary transcript. When a sequence including the signal peptide and first 8 residues in the mature enzyme or the entire PLA(2) (including the signal peptide) was fused to enhanced green fluorescent protein, the fusion protein was directed to the secretory pathway rather than mitochondria in baby hamster kidney (BHK) cells. To examine the role of group IIA PLA(2) in cell injury, wild type (wt) rat group IIA PLA(2) and a mutant group IIA PLA(2) containing a His-47 --> Gln mutation (at the catalytic center) were transfected into BHK cells and cells stably expressing these constructs were isolated. After deprivation of growth factors, both normal BHK cells and BHK cells expressing mutant PLA(2) underwent massive apoptosis, while BHK cells expressing wt PLA(2) showed considerable resistance to growth factor withdrawal-induced apoptosis. The secretory PLA(2) inhibitors 12-epi-scalaradial and aristolochic acid abrogated resistance to apoptosis in the wt PLA(2) expressing cells. These two inhibitors did not induce cell death in the presence of fetal bovine serum, suggesting that they induce cell death by blocking PLA(2) generated survival signals. This study demonstrates that group IIA PLA(2) generates anti-apoptotic survival signals in BHK cells targeting the secretory pathway, and suggests that high levels of group IIA PLA(2) accumulated at inflammatory sites may not only regulate inflammation, but also may protect cells from unnecessary death induced by pro-inflammatory agents.

Alternative Splicing↗
PubMed1999

[Underestimation of medical activity measured by daily activity scores].

OBJECTIVES: To assess the effectiveness of a scoring system (omega) for medical activity. METHODS: In 100 consecutive patients (phase A), the omega scores were calculated by the physician in charge and controlled by an independent physician. In 100 additional patients, the omega scores were controlled again while using corrective measures (phase B). RESULTS: Phase A: at least one item was forgotten in 54% of the stays. The amount of medical activity lost (MAL) was 14 +/- 13%. Phase B: there was no significant reduction in the number of stays with forgotten items (45%, p = 0.41 vs phase A) and the MAL was 17 +/- 16% (p = 0.19 vs 6 +/- 10 days, p = 0.002) and high omega II score (items recorded every time they are performed) (0.8 +/- 1.3 vs 0.4 +/- 0.7, p = 0.01) were associated with forgetting items. The MAL was negatively correlated with the length of stay (r = -0.69, p < 0.001) and omega score (r = -0.40, p = 0.001). CONCLUSION: In routine practice, scoring systems may underestimate medical activity.

Activities of Daily Living↗
PubMed1999

The mitochondrial permeability transition mediates both necrotic and apoptotic death of hepatocytes exposed to Br-A23187.

A23187 and related Ca2+ ionophores are widely used to study Ca2+-dependent cell injury. Here, using laser scanning confocal microscopy and parameter-indicating fluorophores, we investigated the role of the mitochondrial permeability transition (MPT) in Br-A23187 toxicity to cultured rat hepatocytes. After 10 microM Br-A23187, over 60% of hepatocytes lost viability within 1 h. This necrotic cell killing was preceded by increased mitochondrial free Ca2+, mitochondrial depolarization, and onset of the MPT. Cyclosporin A (CsA), a blocker of the permeability transition pore, prevented the MPT and cell killing but had no effect on increased mitochondrial free Ca2+ and depolarization after Br-A23187. To determine whether Br-A23187-induced cell killing was linked to loss of cellular ATP supply, hepatocytes were incubated with fructose and oligomycin, a source of glycolytic ATP and an inhibitor of the uncoupler-stimulated mitochondrial ATPase, respectively. Fructose plus oligomycin prevented cell killing after Br-A23187 but not the MPT. When fructose plus oligomycin prevented necrotic cell killing, apoptosis developed after 10 h. When cells were treated additionally with CsA, these apoptotic changes were prevented. In conclusion, the MPT mediates Br-A23187 cytotoxicity. Acutely, the MPT causes mitochondrial uncoupling and profound ATP depletion, which leads to necrotic cell death. However, when glycolytic ATP generation is available, the MPT induces apoptosis. CsA blocks the MPT and prevents both necrotic and apoptotic cell killing after Br-A23187.

Adenosine Triphosphate↗
PubMed1999

Novel mutant green fluorescent protein protease substrates reveal the activation of specific caspases during apoptosis.

BACKGROUND: The caspase-mediated proteolysis of many cellular proteins is a critical event during programmed cell death or apoptosis. It is important to determine which caspases are activated in mammalian cells, and where and when activation occurs, upon receipt of specific death stimuli. Such information would be useful in the design of strategies to regulate the activation of caspases during apoptosis. RESULTS: We developed two novel fluorescent substrates that were specifically cleaved by caspase-1 or caspase-3. For in vitro studies, four-amino-acid recognition sequences, YVAD for caspase-1 and DEVD for caspase-3, were introduced between blue fluorescent protein (BFP) and green fluorescent protein (GFP), expressed in bacteria and purified. For in vivo studies, YVAD and DEVD were introduced between cyan fluorescent protein and yellow fluorescent protein, and expression was monitored in live mammalian cells. The proximity between fluorophores was determined using fluorescence resonance energy transfer. Purified substrates were cleaved following exposure to purified caspase-1 and caspase-3. In Cos-7 cells, caspase-1 and caspase-3 substrates were cleaved upon induction of apoptosis with staurosporine, a protein-kinase inhibitor, whereas caspase-3 but not caspase-1 substrate was cleaved upon treatment of cells with the DNA-damaging agent mitomycin c. CONCLUSIONS: These substrates allow the spatial activation of specific members of the caspase family to be deciphered during the initiation and execution phase of programmed cell death, and allow activation of specific caspases to be monitored both in vivo and in vitro. This technology is also likely to be useful for high-throughput screening of reagents that modulate caspase activity.

Animals↗