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PubMed1997

Retrovirally transduced human dendritic cells express a normal phenotype and potent T-cell stimulatory capacity.

Dendritic cells are attractive candidates for vaccine-based immunotherapy because of their potential to function as natural adjuvants for poorly immunogenic proteins derived from tumors or microbes. In this study, we evaluated the feasibility and consequences of introducing foreign genetic material by retroviral vectors into dendritic cell progenitors. Proliferating human bone marrow and cord blood CD34+ cells were infected by retroviral vectors encoding the murine CD2 surface antigen. Mean transduction efficiency in dendritic cells was 11.5% from bone marrow and 21.2% from cord blood progenitors. Transduced or untransduced dendritic cell progeny expressed comparable levels of HLA-DR, CD83, CD1a, CD80, CD86, S100, and p55 antigens. Granulocytes, macrophages, and dendritic cells were equally represented among the transduced and mock-transduced cells, thus showing no apparent alteration in the differentiation of transduced CD34+ precursors. The T-cell stimulatory capacity of retrovirally modified and purified mCD2-positive allogeneic or nominal antigen-pulsed autologous dendritic cells was comparable with that of untransduced dendritic cells. Human CD34+ dendritic cell progenitors can therefore be efficiently transduced using retroviral vectors and can differentiate into potent immunostimulatory dendritic cells without compromising their T-cell stimulatory capacity or the expression of critical costimulatory molecules and phenotypic markers. These results support ongoing efforts to develop genetically modified dendritic cells for immunotherapy.

Antigen-Presenting Cells↗

PubMed1997

Development of a novel selective amplifier gene for controllable expansion of transduced hematopoietic cells.

To overcome the low efficiency of gene transfer into hematopoietic cells, we developed a novel system for selective expansion of transduced cells. To this end, we constructed a chimeric cDNA (GCRER) encoding the fusion protein between the granulocyte colony-stimulating factor receptor (G-CSFR) and the hormone-binding domain (HBD) of the estrogen receptor (ER) as a selective amplifier gene. Use of the intracellular signaling pathway of G-CSFR was considered to be appropriate, because G-CSF has the ability not only to stimulate the neutrophil production, but also to expand the hematopoietic stem/progenitor cell pool in vivo. To activate the exogenous G-CSFR signal domain selectively, the estrogen/ER-HBD system was used as a molecular switch in this study. When the GCRER gene was expressed in the interleukin-3 (IL-3)-dependent murine cell line, Ba/F3, the cells showed IL-3-independent growth in response to G-CSF or estrogen. Moreover, the Ba/F3 cells transfected with the Delta(5-195)GCRER, whose product lacks the extracellular G-CSF-binding domain, did not respond to G-CSF, but retained the ability for estrogen-dependent growth. Further, murine bone marrow cells transduced with the GCRER or Delta(5-195)GCRER gene with retroviral vectors formed a significant number of colonies in response to estrogen, as well as G-CSF, whereas estrogen did not stimulate colony formation by untransduced murine bone marrow cells. It is noteworthy that erythroid colonies were apparently formed by the bone marrow cells transduced with the GCRER gene in the presence of estrogen without the addition of erythropoietin, suggesting that the signals from the G-CSFR portion of the chimeric molecules do not preferentially induce neutrophilic differentiation, but just promote the differentiation depending on the nature of the target cells. We speculate that when the selective amplifier genes are expressed in the primitive hematopoietic stem cells, the growth signal predominates and that the population of transduced stem cells expands upon estrogen treatment, even if some of the cells enter the differentiation pathway. The present study suggests that this strategy is applicable to the in vivo selective expansion of transduced hematopoietic stem cells.

Animals↗

PubMed1998

Sustained gene expression in retrovirally transduced, engrafting human hematopoietic stem cells and their lympho-myeloid progeny.

Inefficient retroviral-mediated gene transfer to human hematopoietic stem cells (HSC) and insufficient gene expression in progeny cells derived from transduced HSC are two major problems associated with HSC-based gene therapy. In this study we evaluated the ability of a murine stem cell virus (MSCV)-based retroviral vector carrying the low-affinity human nerve growth factor receptor (NGFR) gene as reporter to maintain gene expression in transduced human hematopoietic cells. CD34(+) cells lacking lineage differentiation markers (CD34(+)Lin-) isolated from human bone marrow and mobilized peripheral blood were transduced using an optimized clinically applicable protocol. Under the conditions used, greater than 75% of the CD34(+) cell population retained the Lin- phenotype after 4 days in culture and at least 30% of these expressed a high level of NGFR (NGFR+) as assessed by fluorescence-activated cell sorter analysis. When these CD34(+)Lin-NGFR+ cells sorted 2 days posttransduction were assayed in vitro in clonogenic and long-term stromal cultures, sustained reporter expression was observed in differentiated erythroid and myeloid cells derived from transduced progenitors, and in differentiated B-lineage cells after 6 weeks. Moreover, when these transduced CD34(+)Lin-NGFR+ cells were used to repopulate human bone grafts implanted in severe combined immunodeficient mice, MSCV-directed NGFR expression could be detected on 37% +/- 6% (n = 5) of the donor-type human cells recovered 9 weeks postinjection. These findings suggest potential utility of the MSCV retroviral vector in the development of effective therapies involving gene-modified HSC.

Animals↗

PubMed1998

Ex-vivo gene therapy using cytokine-transduced tumor vaccines: molecular and clinical pharmacology.

Whether the current generation of cytokine gene-transduced tumor vaccines will show clinical efficacy is under study. Fortunately, the large safety profile so far observed with gene-transduced tumor vaccines can allow outpatient testing in large populations of patients in the adjuvant therapy situation. This will allow large studies statistically powered to see potentially important adjuvant therapy effects in the range that are observed for tamoxifen in breast cancer. For example, the outpatient, adjuvant therapy safety context has been established in the use of GM-CSF gene-transduced autologous prostate cancer vaccines following radical prostatectomy. Similar adjuvant therapy clinical trial efforts are anticipated with allogeneic breast, colon, pancreatic, and ovarian cancer in addition to prostate, renal cell carcinoma, and melanoma. The reverse translation of early clinical data back to basic laboratory research also suggests the field of cytokine gene-transduced tumor vaccine research will remain vibrant. Efforts are currently being directed on optimizing DC activation with polycistronic constructs of cytokine genes, and overexpressing the most relevant tumor-associated peptides. As in the case of antineoplastic drug development, not all lead compounds will become approved drugs in medical oncology. Rigorous yet innovative clinical trial designs will be key to the accelerated identification of cytokine gene-transduced vaccines that improve survival in cancer patients.

Animals↗

PubMed1987

Accuracy and dynamic response of disposable pressure transducer-tubing systems.

Accuracy and dynamic response of seven different disposable saline-filled transducer-tubing systems were evaluated in two configurations; a pole-mount version (60-inch tubing) and patient-mount version (12-inch tubing). Natural frequencies (Fn) and damping coefficients were measured as were pressure waveform recordings. A 0.03 ml air bubble was inserted into the different systems in close proximity to the transducer and measurements were repeated. There were dramatic changes in dynamic response with lengthening of tubing to a pole-mount configuration and air bubble additions. Only one transducer-tubing system had adequate accuracy and dynamic response in both the pole- and patient-mount version. Pressure waveforms in the pole-mount versions and with the air bubble produced systolic overshoots up to 35 mmHg. The performance characteristics dictate that the choice for a disposable transducer-tubing system must be made not only by design, but dynamic response which is directly related to clinical set-up.

Blood Pressure Determination↗

PubMed1979

A new transducer for respiratory monitoring. A description of a hot-wire anemometer and a test procedure for general use.

A respiratory transducer based on the constant temperature anemometry principle has been developed for respiratory monitoring, and as a tool for bedside evaluation of pulmonary function. The transducer is characterized by a dynamic range from 0-2.5 1/s and an upper limiting frequency of 50 Hz. It is designed with a view to a low pressure drop of 2.5 mbar/1/s and a minimum dead space of 5 ml. The transducer has been tested using a generally applicable procedure which includes both static and dynamic test set-ups. The influence of variation in gas composition, temperature and pressure, together with variations in tidal volume and respiration rate, have been investigated. The results show that the transducer registers the immediate value of gas flow-rate with a mean error less than 5-10% in all situations which are predictable in clinical use. The mean error can be reduced to less than 5% when systematic errors are eliminated.

Anesthesia, General↗

PubMed1988

Fiber-optic versus microtip transducers in simultaneous urethrocystometry. A comparative study.

A comparative study of a new fiber-optic transducer versus a microtip transducer was performed in 13 females. A good correlation was found on bladder pressure. The urethral pressure diverged considerably, as the pressures measured with the fiber-optic transducer were about two thirds of the pressures found with the microtip. The functional urethral length measured with the fiber-optic transducer was also shorter.

Adult↗

PubMedDate not supplied

Sweep-frequency marker generator for blood pressure transducer testing.

A circuit which places accurate frequency calibrations on swept-frequency recordings is presented. This circuit is useful in the calibration of direct blood pressure transducers and will have applications in the testing of other biological transducers as well. The design range of 1 Hz to 128 square root 2 Hz is suitable for testing a broad range of biological transducers and systems. The circuit basically measures the periods between successive zero crossings. Pulses are generated that may be recorded on a swept-frequency strip chart record of an individual transducer. A series of sixteen marker pulses indicates 1 Hz, square root 2 Hz, 2 Hz, 2 square root 2 Hz, up to 128 square root 2 Hz. A special wide pulse at 16 Hz distinguishes the marker pulses.

Blood Pressure Determination↗

PubMed1987

[Continuous registration of intracranial pressure using disposable transducers].

The authors report the results of physical tests (baseline drift, temperature drift, absolute accuracy) and clinical experiences in intraventricular intracranial pressure monitoring with disposable transducers. Physical tests gave excellent results concerning baseline drift (less than 1%), temperature drift (0.35 mmHg/degrees C), and absolute accuracy (+/- 2 mmHg) in the range of intracranial pressure of both transducers tested (Gould DTX and Cobe 41-500). Clinical testing gave corresponding values compared with routine methods of ventricular pressure monitoring via a Bentley-Trantec-Transducer. As a result of the study disposable pressure transducers are recommended for routine use in clinical practice of intraventricular intracranial pressure monitoring.

Brain Injuries↗

PubMed1988

Clinical trial of the disposable transducer catheter.

We compared the intracardiac and intravascular pressures obtained by a conventional strain gauge transducer (CT) with a recently developed disposable high-fidelity transducer catheter (DT) during cardiac catheterization. CT was positioned at the patient's midchest level. The pressure measurements obtained by DT compared favorably with those of CT. Femoral arterial pressures by the two methods showed no statistical difference. Right heart pressures were similar using both transducers. However, right ventricular pressures by DT in five of eight patients were lower than that from CT. Higher pulmonary arterial pressures were noted in two of seven patients and higher pulmonary capillary wedge pressures were seen in four patients using DT compared to CT. None of these differences were of statistical significance. These pressure differences may be due to transducer position. Because the midchest position of CT does not precisely define the anatomic location of the cardiac chamber being studied, pressure measurements can be overestimated or underestimated. DT eliminates this problem, as well as overshooting and concern with air bubbles in the catheter system commonly associated with CT. Therefore DT may provide accurate hemodynamic measurements. It would appear to be useful regardless of patient position and may be useful in ambulatory hemodynamic determinations.

Blood Pressure↗

PubMed1991

Correlation between the position of transducers and mitral valve gradient in mitral stenosis.

To assess the severity of mitral stenosis related to the level of transducers, the mitral valve gradient using pulmonary wedge and left ventricle was obtained from 15 patients. The mitral gradient was obtained with both transducers at mid chest level. Then, the level of each transducer was realigned with the catheter tip in the pulmonary capillary wedge and in the left ventricle using lateral fluoroscopy and the mitral gradient was re-measured. At the mid chest level, the mean mitral valve gradient was 14 +/- 6.2 mm Hg with a mitral valve area of 1.3 +/- 0.6 cm2. With the adjusted level of transducers, the mitral valve gradient was 18.7 +/- 6.8 mm Hg with a valve area of 1.0 +/- 0.5 cm2. The difference was that the level of catheter tip in the wedge was 3.5 cm below the mid chest level and the one in the left ventricle was 2.5 cm higher than the mid chest level. This result suggested that the mitral valve gradient obtained at mid chest level underestimated the severity of mitral stenosis.

Cardiac Catheterization↗

PubMed1995

Use of a spherical multiparameter transducer for flow cytometry.

Fused silicon dioxide, multiparameter flow transducers with 50 microns internal square cross section and approximately 60 microns length can simultaneously measure DC and RF impedance as well as fluorescence and multiple-angle light scattering. A spherical version of such a transducer was mounted in an EPICS CVA flow-cell housing and was installed on a research prototype equipped with an argon-ion laser. The signal that was produced by the spherical transducer with EPICS DNA-Check beads was 1.73 times greater than that produced with the standard cylindrical flow cell. Similarly, with EPICS Immuno-Brite beads, the average ratio was 1.96. The Coulter impedance and light-scattering measurements were similar to those produced with the conventional cylindrical outside flow cell, although the internal cross section of the sphere was square and that of the cylinder was circular. The theoretical arguments of Leif and Wells have been demonstrated to be correct. At present, monolithic, spherical fused-silica transducers are the optimal design for combined electrooptical, multiparameter flow cytometry analyzers.

Blood Cells↗

PubMed1980

Transducer beam pattern test object.

A new test object has been developed that generates images of transducer beam patterns on B-mode hardcopy. The extent and depth of the transducer focal zone are measured from these images. The predictions made from test object images were verified in the clinical images obtained from two 3.5-MHz focused transducers. Using the test object images, we have found that we can make a more rational selection of transducer for each clinical situation.

Humans↗

PubMed1991

Endoscopic ultrasound examination of the upper gastrointestinal tract using a curved-array transducer. A preliminary report.

Endoscopic ultrasound examination (EUS) of the upper gastrointestinal (GI) tract for the assessment of mural and extramural pathology has attracted growing international interest in recent years. Since February 1989, EUS has been performed on selected patients in our institution using a new Picker-Pentax fiber-optic ultrasound (US) gastroscope. The instrument consists of a forward-view fiber-optic gastroscope with a 5-MHz curved-array linear US transducer mounted directly behind the lens. The scanning plane lies in the long axis of the scope. Based on in vitro US examinations and EUS of 118 patients over an 18-month period, our preliminary experience with the instrument is described. Using EUS, various lesions in the esophageal wall as well as in the gastric and duodenal walls can be visualized. Furthermore, organs and structures outside the GI tract can be seen, and lesions such as enlarged lymph nodes in the mediastinum and abdomen; solid and cystic masses in the liver, pancreas and retroperitoneum; arterial aneurysms; esophageal varices; and gall stones and calcifications can be demonstrated. The 5-MHz transducer does not provide very detailed information on the GI wall. The direction of the ultrasound scanning planes is difficult to define, as the transducer cannot be seen through the optic lens. The method demands great expertise in endoscopy and ultrasound. Indications for EUS have not been definitively established. Evaluation of the diagnostic accuracy of this technique requires further controlled studies. We believe that EUS using a curved-array linear transducer will provide significant diagnostic information of clinical relevance to gastroenterology.

Aged↗

PubMed1986

An ultrasensitive transducer for measurement of isometric contractile force from single heart cells.

A novel ultrasensitive force transducer suitable for measuring isometric forces generated by single spindle-shaped muscle cells is described. The transducer components are mechanically and electrically simple, consisting of a low power He-Ne laser, a pair of step index, glass optic fibers, and a photodiode detector circuit. To test the operation of the transducer, enzymatically isolated frog ventricular heart cells were used, having peak contractile forces on the order of 100 nN. The transducer presents a number of advantages over existing designs and has a resolution better than 2 nN. As such, it is suitable for excitation-contraction studies in single muscle cells.

Animals↗

PubMed1978

A quarter Wheatstone bridge strain gage force transducer for recording gut motility.

Quarter and half Wheatstone bridge extraluminal force transducers for recording of gastrointestinal motility are compared. Modification of the transducer to a quarter bridge is economical, simplifies construction, and improves longevity by eliminating the crossover wire which frequently short circuits. The quarter bridge transducer was found to be as accurate and sensitive as the half bridge transducer.

Animals↗

PubMed1990

Pressure transducers: an overlooked source of sepsis in the intensive care unit.

Between January 1988 and May 1989 twenty cases of bacteremia due to Flavobacterium sp. occurred in 17 patients admitted to a surgical intensive care unit. Epidemiologic studies disclosed that the source of the Flavobacterium bacteremias was contaminated reusable pressure transducers. Despite the use of disposable domes spread of the bacteria from the contaminated transducer heads to the fluids given to the patients occurred. An indirect contamination by hands at the time the equipment was initially assembled must have been the mode of transmission. Reinstitution of routine disinfection of the transducer heads controlled the outbreak. Disposable domes failed to prevent septicemia from contaminated pressure transducers.

Cross Infection↗

PubMed1990

Effect of air flow and flow transducer on tracheal breath sounds.

Tracheal breath sounds (TBSs) were analysed in 12 normal adult subjects at the air flow levels of 1.6, 2.1 and 2.6 litres-1, using a low-resistance flow transducer, and at an estimated flow of 2.1 litres-1 without the flow transducer. The major findings were that the TBSs were significantly distorted by the flow transducer, but were independent of air flow. We therefore conclude that true TBSs can only really be recorded when an oral flow transducer is not used. The within-subject reproducibility of TBS was relatively good, while the cross-subject comparison of TBS showed that each subject produced their own unique spectral pattern, although the TBSs of normal subjects fall in a common frequency range. Also, inspiratory sounds were significantly lower in peak frequency than expiratory TBSs.

Adult↗