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Biomedical subjects

J Fisher

Publications and source records attributed to J Fisher.

At least 289 records · Page 16Linked to original sources
PubMed1994

Characterization of antibodies to the rat substance P (NK-1) receptor and to a chimeric substance P receptor expressed in mammalian cells.

Antibodies to neuropeptide receptors can be used to localize and characterize the receptors in tissues and cell lines. Two strategies were used to study the rat substance P receptor (SPR, NK-1) by immunological methods. First, a polyclonal antiserum was raised by immunizing rabbits with a peptide corresponding to the 15 amino acid residues (KTMTESSSFYSNMLA, SPR393-407) at the intracellular C-terminus of the rat SPR coupled to bovine thyroglobulin. An antiserum was obtained with a titer for half-maximal binding of 125I-SPR393-407 of 1:70,000. Nonradioactive SPR393-407 inhibited 50% of binding at a concentration of 10 pM. Binding of 125I-SPR393-407 to the antiserum was also displaced in a parallel manner by membrane proteins from tissues expressing high levels of the SPR (brain and submaxillary gland). Second, a chimeric SPR construct of a hydrophilic Flag peptide (DYKDDDDK) genetically engineered in sequence with the extracellular N-terminus of rat SPR was generated by polymerase chain reaction. The Flag-SPR chimera was expressed in rat kidney epithelial cells (KNRK) and judged to be fully functional, assessed by binding of 125I-substance P (apparent Kd of 5.63 nM) and calcium mobilization in response to substance P (EC50 of 0.66 nM). Antibodies to SPR393-407 and the Flag peptide stained the plasma membrane of KNRK cells expressing the native SPR or the Flag-SPR chimera. Staining was abolished by preincubation with SPR393-407 or the Flag peptide. Cells transfected with vector alone were unstained. The SPR antiserum recognized a broad protein band on Western blots of membranes prepared from cells expressing SPR but not from cells transfected with vector alone. The signal was quenched by preincubation of the antiserum with SPR393-407. By immunohistochemistry, the SPR antiserum was found to bind to neurons in the dorsal horn of the rat spinal cord and to ganglion cells in the myenteric plexus of the rat ileum near substance P-immunoreactive nerve fibers. Staining was abolished by preabsorption of the antiserum with SPR393-407. These antibodies can be used to localize the SPR in tissues and cells and to examine the function of the receptor in cell lines.

Amino Acid Sequence↗
PubMed1994

Cycloheximide inhibits the cytotoxicity of paclitaxel (Taxol).

Treatment of human breast (MCF-7) and lung (A549) adenocarcinoma cell lines with 10 micrograms/ml cycloheximide provided substantial protection from paclitaxel-induced cytotoxicity. Addition of cycloheximide to cells at 0, 6, 12 or 18 h into a 24 h exposure to paclitaxel resulted in cytotoxicity similar to that found in cells treated with paclitaxel alone for only 0, 6, 12 or 18 h, respectively. DNA flow cytometry showed that paclitaxel blocked cells in G2/M. Mitotic index studies demonstrated that paclitaxel arrested cells in mitosis and that prolonged exposure to paclitaxel resulted in the development of multiple micronuclei. Concurrent incubation of cells in cycloheximide prevented the development of a G2/M block, mitotic arrest and micronuclei formation. The addition of cycloheximide to cells at 6 or 12 h into a 24 h exposure to paclitaxel reduced the degree of G2/M block to that produced by incubation of cells in paclitaxel alone for only 6 or 12 h. Mitotic index studies confirmed that cells treated with cycloheximide during paclitaxel exposure had a marked reduction in the percentage of cells in mitosis. However, the percentage of paclitaxel-treated cells which had multiple micronuclei was increased in cells treated with cycloheximide. These results indicate that entry into mitosis is a prerequisite for paclitaxel-induced cytotoxicity and that cycloheximide reduces cytotoxicity due to paclitaxel by preventing cells from entering mitosis. However, once cells have entered mitosis in the presence of paclitaxel, protein synthesis is not required for the development of multiple micronuclei and cytotoxicity.

Adenocarcinoma↗
PubMed1994

Sequence dependence of paclitaxel (Taxol) combined with cisplatin or alkylators in human cancer cells.

Clinical trials combining paclitaxel with other active chemotherapy agents are currently underway. In vitro preclinical studies may assist in the selection of appropriate drug combinations or sequences for clinical investigation. We have used clonogenic cell survival assays and DNA flow cytometry to examine the effect of paclitaxel combined with melphalan, thiotepa, or cisplatin on the survival and cell-cycle parameters of human lung A549 and breast MCF-7 adenocarcinoma cells. A549 and MCF-7 cells were incubated with paclitaxel for 24 h, followed by a 1 h exposure to cisplatin, melphalan, or thiotepa. Both cell types were also incubated with cisplatin or an alkylator for 1 h followed by a 24 h paclitaxel exposure. When the paclitaxel exposure preceded either melphalan, thiotepa, or cisplatin, the cytotoxicity was additive for both cell lines tested. When cisplatin or alkylator exposure was given prior to the paclitaxel, cytotoxicity was also additive in MCF-7 cells. However, cisplatin or alkylators were antagonistic to paclitaxel cytotoxicity when they preceded the paclitaxel exposure in A549 cells (e.g., 2% survival with 100 nM paclitaxel vs. 7% survival with cisplatin and paclitaxel). Cell-cycle analysis revealed that exposure to 100 nM paclitaxel for 24 h blocked a majority of the cells into the G2/M phase (> or = 80% for A549 cells, 60-65% for MCF-7 cells). However, exposure to alkylators before incubation in paclitaxel reduced the proportion of A549 but not MCF-7 cells in G2/M--e.g., exposure to 30 micrograms/ml cisplatin prior to paclitaxel exposure caused only 25% of A549 and 55% of MCF-7 cells to block in G2/M.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1994

Biomechanics of glutaraldehyde-treated porcine aortic roots and valves. An investigation of the effect of predilation of the elastic aortic root.

The biomechanics and function of fresh porcine aortic roots and valves have been compared with those of glutaraldehyde-treated roots prepared in a conventional manner without dilation of the elastic aortic root and with glutaraldehyde-treated roots prepared with permanent predilation during fixation. The glutaraldehyde-treated aortic walls were significantly less extensible than fresh walls, with a mean dilation of only 6% compared with 45% for the fresh root at 120 mm Hg pressure. Permanent predilation of the aortic root during fixation allowed the total dilation of the fixed root to be increased to 19% at 120 mm Hg pressure. The effective orifice area of the fresh root and valve was significantly greater than those of the fixed roots and valves, with permanent predilation fixation producing a significantly greater orifice area than conventional fixation. The open-leaflet bending deformations were found to be lower in the valves fixed after permanent predilation than in the standard fixed valves. The glutaraldehyde-treated porcine root and valve does not reproduce the biomechanics and function of the fresh/root, because of the reduced extensibility of the fixed aortic wall. Permanent predilation during fixation helps to partially overcome the shortcomings of the fixed root, producing better function than a standard fixed valve.

Aortic Valve↗
PubMed1994

Comparative study of the hydrodynamic function of the size 19mm and 21mm St. Jude Medical Hemodynamic Plus Bileaflet Heart valves.

The hydrodynamic function of the St. Jude Medical Hemodynamic Plus Bileaflet Heart valve has been compared to the function of the standard St. Jude valve, the Carbomedics, Duromedics and the Monostrut valves in a pulsatile flow simulator. Size 19mm and 21mm tissue annulus diameter valves have been studied for use in small aortic roots. The size 19mm St. Jude hemodynamic Plus had lower forward flow pressure drops and lower total energy losses than the other valves studied. The size 19mm St. Jude Hemodynamic Plus valve should provide lower forward flow pressure drops and energy losses for the patient with a small aortic root, than the other types of prostheses included in the study.

Aortic Valve↗
PubMed1994

The combination of expanders with autogenous tissue in breast reconstruction.

Combining the use of tissue expanders and implants with autogenous tissue techniques of breast reconstruction takes maximal advantage of the benefits associated with each method. This approach provides an additional reconstructive option that is particularly useful in patients who are not ideal candidates for either method alone. Reconstruction may be performed in an immediate or delayed fashion, and the aesthetic results are excellent.

Female↗
PubMed1993

Taxol in combination with doxorubicin or etoposide. Possible antagonism in vitro.

BACKGROUND: Taxol is a novel chemotherapeutic agent that promotes microtubule assembly and stabilizes tubulin polymer formation. Clinical evaluation of its antineoplastic activity as a single agent and in combination with other chemotherapeutic drugs is in progress. METHODS: To evaluate the effect of combining taxol with other commonly used antineoplastic agents, clonogenic survival of human breast cancer MCF7 cells, human lung adenocarcinoma A549 cells, and human ovarian cancer OVG1 cells were assayed after an initial exposure to taxol for 24 hours (approximately LD90 for taxol), followed by a 1-hour incubation with varying concentrations of doxorubicin or etoposide (total taxol incubation time, 25 hours). RESULTS: When corrected for taxol-induced cytotoxicity, doxorubicin and etoposide caused less cell killing in the presence of taxol compared with control incubations of doxorubicin and etoposide alone. To determine if a different schedule of drug application resulted in a similar finding, MCF7, A549, and OVG1 cells were exposed to doxorubicin for 1 hour, followed by incubation with varying concentrations of taxol for 24 hours. Less-than-additive cytotoxicity for the combination of taxol and doxorubicin was found. Flow cytometry studies in MCF7 cells showed that taxol caused a G2/M cell cycle block. Fewer cells were found to be in S-phase, which is the most doxorubicin-sensitive phase of the cell cycle. The application of doxorubicin or etoposide to MCF7 cells for 1 hour resulted in partial G1 and G2/M cell cycle blocks. Fewer cells were found to be moving through the cell cycle, which is likely required for taxol cytotoxicity. CONCLUSION: Although direct antagonism of the cytotoxicity of doxorubicin or etoposide by taxol has not been proven, there is less-than-additive in vitro cytotoxicity when taxol is combined with these chemotherapeutic agents. The clinical implications of these findings are unknown; however, these findings generate concern about the combination of these agents in clinical trials and suggest that additional studies to determine optimal scheduling are needed.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Structural and dynamic studies of a non-self-complementary dodecamer DNA duplex.

A non-self-complementary dodecamer duplex d(CCTAAATTTGCC).d(GGCAAATTTAGG) has been investigated in solution by high resolution 1H NMR. Almost complete resonance assignment of both non-exchangeable and exchangeable protons, has been achieved. The duplex is essentially B-type, with distortions apparent at the AT and TA steps. These distortions and their affects on dynamics have been probed by the measurement of base-pair lifetimes, and observation of water of hydration. Base-pair opening rates were derived from measurements of T1's and effects on linewidths of the T and G imino protons on addition of an exchange catalyst. Our results are generally in line with observations reported for other systems, but we see only a slight drop in the A.T base-pair lifetime on moving out from the central region. This observation is reinforced by the detection of DNA-water nOe's for residues distributed throughout the dodecamer sequence.

Base Sequence↗
PubMed1993

Pharmacokinetics, absorption, distribution and disposition of [125I]-defibrotide following intravenous or oral administration in the rat.

Defibrotide (D) was labelled with 125I. The radiolabelled compound ([125I]-Defibrotide ([125I]-D)) retained the same profibrinolytic activity as the parent drug. Following single intravenous administration of [125I]-D the half lives of radioactivity associated with D components in plasma were 9.45 min and 11.27 h for alpha and beta phases respectively. Following single oral administration of [125I]-D the half life of radioactivity associated with D components in plasma was 12.83 h for the elimination phase. Bioavailability was apparently 58%. The areas under plasma total radioactivity versus time curves were dose-dependent following both intravenous and oral administration. No significant accumulation of total radioactivity in plasma was observed following multiple oral administration of [125I]-D. Following single intravenous administration of [125I]-D a larger proportion of administered radioactivity was excreted via urine than faeces while following single oral administration excretion via urine and faeces accounted for similar proportions of administered radioactivity. Following both single and oral administration the levels of total radioactivity in tissues and organs examined were generally highest in highly perfused organs and were very high in the thyroid despite pretreatment with non-radiolabelled potassium iodide. Radioactivity was also found to be associated with the aorta wall.

Absorption↗
PubMed1993

An intraoperative patient stabilization device.

An intraoperative patient stabilization device is described for use in aesthetic breast surgery. This simple device maintains the patient in the vertical position throughout the many positional changes during aesthetic breast surgery.

Female↗
PubMed1993

The children of divorce parenting intervention: outcome evaluation of an empirically based program.

Examined efficacy of an empirically based intervention using 70 divorced mothers who participated in a 12-session program or a wait-list condition. The program targeted five putative mediators: quality of the mother-child relationship, discipline, negative divorce events, contact with fathers, and support from nonparental adults. Posttest comparisons showed higher quality mother-child relationships and discipline, fewer negative divorce events, and better mental health outcomes for program participants than controls. More positive program effects occurred for mothers' than children's reports of variables and for families with poorest initial levels of functioning. Analyses indicated that improvement in the mother-child relationship partially mediated the effects of the program on mental health.

Adaptation, Psychological↗
PubMed1993

Geometry of homograft valve leaflets: effect of dilation of the aorta and the aortic root.

With the increasing interest in aortic homografts as either a free-sewn valve or whole-root replacement, the effect of internal pressure and dilation of the aorta and aortic root on valve leaflet geometry has been studied. Seven aortic homograft roots were studied, six that had been stored in antibiotics and one that had been cryopreserved. The diameter of the aorta was determined as a function of internal pressure and correlated with the stress-strain characteristics of the aortic wall. Three-dimensional leaflet surface geometry was measured in the "neutral" position, and the leaflet was characterized by its radius of curvature and angle of inclination, using a cylindrical model. The diameter of the aorta increased by between 30% and 50% as the dilation pressure increased from 0 to 120 mm Hg. This was consistent with the stress-strain data obtained from strips of the aortic wall in the circumferential direction. The angle of inclination of the leaflet increased from 20 to 80 degrees and the radius of curvature increased from 4 to 17 mm as the internal pressure increased from 0 to 80 mm Hg. The open leaflet configuration showed a triangular orifice with low bending strains for a dilated root, but increased bending strains with reduced dilation pressure. These are important considerations when implanting a free-sewn homograft into the aortic root.

Adult↗
PubMed1993

The postingestive consequences of fat condition preferences for flavors associated with high dietary fat.

To investigate whether children acquire conditioned preferences for flavors associated with high dietary fat content, 27 3- and 4-year-old children participated in a series of 12 conditioning or mere exposure sessions. Following an overnight fast, children who participated in conditioning trials consumed fixed quantities of a flavored yogurt drink that on half the days was high in fat and energy (954 kJ, 18 g fat/150 g serving) or contained no fat (277 kJ, 0 g fat/150 g serving). Children in the conditioning group consumed 150 g servings, children in the mere exposure group tasted 16 g or less of these same stimuli. Preferences were assessed before and after conditioning when the children were hungry and also postconditioning when the children were satiated. Results provided evidence for conditioned preferences based on the postingestive consequences of dietary fat. Children in the conditioning group learned to prefer the high-density paired flavor over the low-density paired flavor, and increased their preference for the high-density paired flavor from pre- to postconditioning. Children in the mere exposure group showed positive shifts in preference for both the fat-free and the high-fat paired flavors. In the conditioning group, preferences for the high-fat flavor was depressed by satiety, whereas the preference of the mere exposure group did not vary with hunger state. Conditioned flavor preferences, based on the postingestive consequences of fat intake, may contribute to children's preferences for foods high in dietary fat.

Association Learning↗
PubMed1993

Comparative study of the function of the Abiomed polyurethane heart valve for use in left ventricular assist devices.

Hydrodynamic testing of the Abiomed polyurethane trileaflet valve has been carried out to establish performance data of valve function. A Medtronic Hall tilting disk, a Carbomedics bileaflet, a Hancock II bioprosthesis and an Abiomed polyurethane trileaflet valve, all size 27 mm, underwent both pulsatile and steady-flow hydrodynamic testing. Results of the variation of pressure difference with RMS pulsatile flow and steady flow, and effective orifice area, showed that the Abiomed valve had significantly poorer opening characteristics than the tissue valve and the two mechanical valves. The Abiomed valve's performance was seen to be related to its construction and manufacture. This study highlights some of the problems associated with the design and development of synthetic trileaflet heart valve prostheses.

Biocompatible Materials↗
PubMed1993

Genitourinary malformations associated with agenesis of the corpus callosum.

Agenesis of the corpus callosum is an infrequent congenital anomaly that occurs in partial or complete forms, and is frequently associated with other craniofacial and skeletal abnormalities. An increased association with genitourinary abnormalities has not been previously defined. We reviewed the records of 22 boys and 11 girls with agenesis of the corpus callosum. Of the patients 18 had complete radiological or necroscopic evaluation and 15 had physical examinations as the sole means of evaluation. Renal anomalies were the most frequent genitourinary abnormalities identified in these children, although ureteral, genital and bladder abnormalities were also encountered. There was an exceptionally high incidence of undescended testes (23%), approximately 20-fold greater than the frequency in the normal population, possibly resulting from hypothalamic insufficiency associated with midline cranial defects. We suggest, therefore, that all patients with agenesis of the corpus callosum should be thoroughly evaluated with bladder and renal ultrasound studies to rule out any genitourinary abnormalities. Male patients with agenesis of the corpus callosum and undescended testes should undergo hypothalamic/pituitary axis testing.

Abnormalities, Multiple↗