PROGRAMMABLE DIELECTROPHORETIC μTAS SAMPLE HANDLING

We present the concept of a general-purpose sample analysis platform (GSAP) based on dielectrophoretic methods. The platform architecture comprises integrated functional blocks that can be programmed to perform a diverse range of analysis steps, including the on-device preparation of real world samples.

Synthesis, electrophilic substitution and structure-activity relationship studies of polycyclic aromatic compounds towards the development of anticancer agents

Polycyclic aromatic hydrocarbons (PAH) are considered potentially carcinogenic. Substituted PAH derivatives, in contrast, may serve as anticancer agents, and as chemotherapeutics. This article presents a review of their use. Particular emphasis is placed on the synthesis of these new compounds, electrophilic substitution reactions and novel synthetic methodologies developed in our laboratory. Based on numerous reports and the data available, we believe that DNA-intercalating and membrane-interacting sites are the target for their effects.

Polycyclic aromatic compounds as anticancer agents: structure-activity relationships of chrysene and pyrene derivatives

A large number of diamides and diamines were synthesized using 6-amino chrysene and 1-amino pyrene as starting materials. A structure activity study with cis-platinum as internal control against animal and human tumor lines was carried out in vitro. This study indicated that the in vitro cytotoxicity toward these lines depends on the functionality present in the molecules. The diamino compounds were found to be more potent than the diamides, and these were equally active irrespective of the end heterocyclic group, whereas the activity of the diamides was strongly dependent on the terminal unit. In general, the diamides containing chrysene as the chromophore were more active than those with a pyrene ring. The size of the end heterocyclic ring, along with the nature of the spacer connecting the polycyclic ring to the heterocyclic ring, seemed to affect the biological activity in certain cell lines. Hemolysis experiments on a lead compound established that it had activities similar to those described for membrane-stabilizing agents. This agent also demonstrated the capacity to produce differentiation in leukemia cell lines.

Polycyclic aromatic compounds as anticancer agents: synthesis and biological evaluation of dibenzofluorene derivatives

Highly regioselective electrophilic substitution of dibenzofluorene was achieved and the nitro derivative was transformed to a variety of new anticancer agents.

Differential analysis of human leukocytes by dielectrophoretic field-flow-fractionation

The differential analysis of human leukocytes has many important biological and medical applications. In this work, dielectrophoretic field-flow-fractionation (DEP-FFF), a cell-separation technique that exploits the differences in the density and dielectric properties of cells, was used to separate the mixtures of the major human leukocyte subpopulations (T- and B-lymphocytes, monocytes, and granulocytes). The separation was conducted in a thin chamber equipped with an array of microfabricated interdigitated electrodes on the bottom surface, and the separation performance was characterized by on-line flow cytometry. To investigate optimal separation conditions for different leukocyte mixtures, elution fractograms at various DEP field frequencies were obtained for each leukocyte subtype. With appropriately chosen conditions, high separation performance was achieved in separating T- (or B-) lymphocytes from monocytes, T- (or B-) lymphocytes from granulocytes, and monocytes from granulocytes. DEP-FFF does not involve cell-labeling or cell-modification step, and provides a new approach to hematological analysis.

The removal of human breast cancer cells from hematopoietic CD34+ stem cells by dielectrophoretic field-flow-fractionation

Dielectrophoretic field-flow-fractionation (DEP-FFF) was used to purge human breast cancer MDA-435 cells from hematopoietic CD34+ stem cells. An array of interdigitated microelectrodes lining the bottom surface of a thin chamber was used to generate dielectrophoretic forces that levitated the cell mixture in a fluid flow profile. CD34+ stem cells were levitated higher, were carried faster by the fluid flow, and exited the separation chamber earlier than the cancer cells. Using on-line flow cytometry, efficient separation of the cell mixture was observed in less than 12 min, and CD34+ stem cell fractions with a purity >99.2% were obtained. The method of DEP-FFF is potentially applicable to many biomedical cell separation problems, including microfluidic-scale diagnosis and preparative-scale purification of cell subpopulations.

Dielectric properties of human leukocyte subpopulations determined by electrorotation as a cell separation criterion

The separation and purification of human blood cell subpopulations is an essential step in many biomedical applications. New dielectrophoretic fractionation methods have great potential for cell discrimination and manipulation, both for microscale diagnostic applications and for much larger scale clinical problems. To discover whether human leukocyte subpopulations might be separable by such methods, the dielectric characteristics of the four main leukocyte subpopulations, namely, B- and T-lymphocytes, monocytes, and granulocytes, were measured by electrorotation over the frequency range 1 kHz to 120 MHz. The subpopulations were derived from human peripheral blood by magnetically activated cell sorting (MACS) and sheep erythrocyte rosetting methods, and the quality of cell fractions was checked by flow cytometry. Mean specific membrane capacitance values were calculated from the electrorotation data as 10.5 (+/- 3.1), 12.6 (+/- 3.5), 15.3 (+/- 4.3), and 11.0 (+/- 3.2) mF/m2 for T- and B-lymphocytes, monocytes, and granulocytes, respectively, according to a single-shell dielectric model. In agreement with earlier findings, these values correlated with the richness of the surface morphologies of the different cell types, as revealed by scanning electron microscopy (SEM). The data reveal that dielectrophoretic cell sorters should have the ability to discriminate between, and to separate, leukocyte subpopulations under appropriate conditions.

Cell separation on microfabricated electrodes using dielectrophoretic/gravitational field-flow fractionation

Dielectrophoretic/gravitational field-flow fractionation (DEP/G-FFF) was used to separate cultured human breast cancer MDA-435 cells from normal blood cells mixed together in a sucrose/dextrose medium. An array of microfabricated, interdigitated electrodes of 50 microns widths and spacings, and lining the bottom surface of a thin chamber (0.42 mm H x 25 mm W x 300 mm L), was used to generate DEP forces that levitated the cells. A 10-microL cell mixture sample containing approximately 50,000 cells was introduced into the chamber, and cancerous and normal blood cells were levitated to different heights according to the balance of DEP and gravitational forces. The cells at different heights were transported at different velocities under the influence of a parabolic flow profile that was established in the chamber and were thereby separated. Separation performance depended on the frequency and voltage of the applied DEP field and the fluid-flow rate. It took as little as 5 min to achieve cell separation. An analysis of the DEP/G-FFF results revealed that the separation exploited the difference in dielectric and density properties between cell populations. The DEP/G-FFF technique is potentially applicable to many biological and biomedical problems, especially those related to microfluidic systems.

Membrane dielectric responses of human T-lymphocytes following mitogenic stimulation

Human peripheral blood T-lymphocytes, normally resting at the G0 phase, were stimulated with phytohemagglutinin (PHA) and interleukin-2 (IL-2) to induce the cell division cycle. The cells were examined at 24-h intervals for up to 96 h by flow cytometry to determine cell cycle distributions and by electrorotation to determine dielectric properties. The average membrane specific capacitance was found to vary from 12 (+/-1.5) mF/m2 prior to stimulation to 10 (+/-1.5) and 16 (+/-3.5) mF/m2 at 24 and 48 h after stimulation, respectively, and to remain unchanged up to 96 h after stimulation. Scanning electron microscopy studies of the cells revealed an increased complexity in cell membrane morphology following stimulation, suggesting that the observed change in the membrane capacitance was dominated by the alteration of cell surface structures. The average electrical conductivity of the cell interior decreased from approximately 1.1 S/m prior to stimulation to approximately 0.8 S/m at 24 h after stimulation and showed little change thereafter. The average dielectric permittivity of the cell interior remained almost unchanged throughout the course of the cell stimulation. The percentage of T-lymphocytes in the S and G2/M phases increased from approximately 4% prior to stimulation to approximately 11 and approximately 34% at 24 and 48 h after stimulation, respectively. The large change in membrane specific capacitance between the 24 and 48 h time period coincided with the large alteration in the cell cycle distribution where the S and G2/M populations increased by approximately 23%. These data, together with an analysis of the variation of the membrane capacitance during the cell cycle based on the cell cycle-dependent membrane lipid accumulation, show that there is a correlation between membrane capacitance and cell cycle phases that reflects alterations in the cell plasma membrane.

Modification of the subunit principle for reconstruction of nasal tip and dorsum defects

This article reports our observations on, and modification of, the subunit principle with regard to reconstruction of nasal tip and dorsum defects. Forty-two patients who underwent reconstruction of a nasal tip and/or dorsum defect with a forehead flap were reviewed. These patients were categorized by how the subunit principle was used in their reconstruction and graded on the aesthetic outcome of the reconstruction. We found that the patients who had both the nasal tip and dorsum replaced obtained better results than those who had just 1 subunit replaced (P = .008). Review of postoperative photographs shows that the reason for this discrepancy in aesthetic outcomes is the line of transition between the forehead skin and remaining nasal skin if only 1 subunit is replaced. With this observation in mind, we feel that patients undergoing reconstruction of the nasal tip and/or dorsum should be evaluated for discrepancies in tissue type between the recipient nasal site and forehead donor site. If the tissues are noted to be significantly disparate, the reconstructive surgeon may consider replacing both subunits with a single forehead flap.

Polycyclic aromatic compounds as anticancer agents: synthesis and biological evaluation of some chrysene derivatives

Synthesis and biological evaluation of new chrysene derivatives aimed at the development of anticancer agents were carried out.

Separation of polystyrene microbeads using dielectrophoretic/gravitational field-flow-fractionation

The characterization of a dielectrophoretic/gravitational field-flow-fractionation (DEP/G-FFF) system using model polystyrene (PS) microbeads is presented. Separations of PS beads of different surface functionalization (COOH and none) and different sizes (6, 10, and 15 microm in diameter) are demonstrated. To investigate the factors influencing separation performance, particle elution times were determined as a function of particle suspension conductivity, fluid flow rate, and applied field frequency and voltage. Experimental data were analyzed using a previously reported theoretical model and good agreement between theory and experiment was found. It was shown that separation of PS beads was based on the differences in their effective dielectric properties. Particles possessing different dielectric properties were positioned at different heights in a fluid-flow profile in a thin chamber by the balance of DEP and gravitational forces, transported at different velocities under the influence of the fluid flow, and thereby separated. To explore hydrodynamic (HD) lift effects, velocities of PS beads were determined as a function of fluid flow rate in the separation chamber when no DEP field was applied. In this case, particle equilibrium height positions were governed solely by the balance of HD lift and gravitational forces. It was concluded that under the experimental conditions reported here, the DEP force was the dominant factor in controlling particle equilibrium height and that HD lift force played little role in DEP/G-FFF operation. Finally, the influence of various experimental parameters on separation performance was discussed for the optimization of DEP/G-FFF.

Electrorotation of liposomes: verification of dielectric multi-shell model for cells

The reliability of multi-shell dielectric models, used to describe the ac electrokinetic behaviour of cells, has been tested by performing electrorotation and dielectrophoretic measurements on unilamellar, oligolamellar, and multilamellar liposomes of diameters ranging from 5 to 24 microm. Fluorescence microscopy, flow cytometry and electron spin resonance were used to characterise the morphology and membranes of the liposomes. The dielectric properties of the various types of liposomes, based on appropriate dielectric shell models, were then analysed using a general purpose, recursive, algorithm. Through simulations, the confidence levels that can be assigned to parameters derived through application of simple shell models are estimated. From this, we confirm that electrorotation data enable accurate determinations to be made of the dielectric properties of the outermost membrane of liposomes, and provide good indications of the level of complexity of the shells and internal compartments. We also demonstrate that, used with sufficient additional information, such as that provided by dielectrophoresis, electrorotation data yields unique solutions for the dielectric parameters of liposome-like particles.

Introducing dielectrophoresis as a new force field for field-flow fractionation

We present the principle of cell characterization and separation by dielectrophoretic field-flow fractionation and show preliminary experimental results. The operational device takes the form of a thin chamber in which the bottom wall supports an array of microelectrodes. By applying appropriate AC voltage signals to these electrodes, dielectrophoretic forces are generated to levitate cells suspended in the chamber and to affect their equilibrium heights. A laminar flow profile is established in the chamber so that fluid flows faster with increasing distance from the chamber walls. A cell carried in the flow stream will attain an equilibrium height, and a corresponding velocity, based on the balance of dielectrophoretic, gravitational, and hydrodynamic lift forces it experiences. We describe a theoretical model for this system and show that the cell velocity is a function of the mean fluid velocity, the voltage and frequency of the signals applied to the electrodes, and, most significantly, the cell dielectric properties. The validity of the model is demonstrated with human leukemia (HL-60) cells subjected to a parallel electrode array, and application of the device to separating HL-60 cells from peripheral blood mononuclear cells is shown.

Secondary healing of Mohs defects of the forehead, temple, and lower eyelid

OBJECTIVE

To analyze the results of secondary healing of Mohs defects of the forehead, temple, and lower eyelid.

DESIGN

Scars resulting from secondary healing in these 3 sites were rated by patient interviews and by analysis of postoperative photographs by 3 board-certified members of the American Academy of Facial Plastic and Reconstructive Surgery.

SETTING

Private facial plastic and reconstructive surgery practice in Florida.

PATIENTS

Patients with Mohs wounds of the forehead, temple, and lower eyelid that were allowed to heal by secondary intention between January 1, 1989, and December 31, 1993, who were available for follow-up. There were 10 wounds of the forehead, 6 of the temple, and 10 of the lower eyelid that were available for analysis.

MAIN OUTCOME MEASURES

Wound color, contour, distortion of surrounding structures, presence of telangiectasias or paresthesias, pain or infection during healing, and overall cosmetic result.

RESULTS

Color, contour, and overall scar cosmesis were rated using the following scale: poor (0), fair (1), good (2), and excellent (3). Telangiectasias, paresthesias, and pain or infection during healing were recorded as present or absent. The respective color and contour ratings for the 3 sites were 2.2 and 2.2 for the forehead, 2.5 and 2.7 for the temple, and 2.7 and 3 for the lower eyelid according to patient interview and 1 and 1.3 for the forehead, 1 and 1.4 for the temple, and 2.6 and 2.5 for the lower eyelid according to surgeon analysis. Pain, infection, paresthesias, and distortion of surrounding structures were rare, but 7 of 10 forehead and 4 of 6 temple wounds had telangiectasias.

CONCLUSIONS

Many defects of the forehead and temple will heal with acceptable results. Partial-thickness or small full-thickness lower eyelid wounds heal with excellent cosmetic and functional results. Patient satisfaction is greater than might be predicted by surgeon analysis of wound healing.

Dielectrophoretic manipulation of cells with spiral electrodes

Electrokinetic responses of human breast cancer MDA-MB-231 cells were studied in suspensions of conductivities 18, 56, and 160 mS/m on a microelectrode array consisting of four parallel spiral electrode elements energized with phase-quadrature signals of frequencies between 100 Hz and 100 MHz. At low frequencies cells were levitated and transported toward or away from the center of the spiral array, whereas at high frequencies cells were trapped at electrode edges. The frequencies of transition between these characteristic cell behaviors increased with increasing suspension conductivity. Levitation heights and radial velocities were determined simultaneously for individual cells as a function of the applied field magnitude and frequency. Results were compared with theoretical predictions from generalized dielectrophoresis theory applied in conjunction with cell dielectric parameters and simulated electric field distributions corrected for electrode polarization effects. It was shown that the conventional and traveling-wave dielectrophoretic force components dominated cell levitation and radial motion, respectively. Both theoretical predictions and experimental data showed that the cell radial velocity was very sensitive to the field frequency when the in-phase component of the field-induced polarization was close to zero. Applications of spiral electrode arrays, including the isolation of cells of clinical relevance, are discussed.

Dielectrophoretic detection of changes in erythrocyte membranes following malarial infection

The dielectric properties of normal erythrocytes were compared to those of cells infected with the malarial parasite Plasmodium falciparum. Normal cells provided stable electrorotation spectra which, when analyzed by a single-shelled oblate spheroid dielectric model, gave a specific capacitance value of 12 +/- 1.2 mF/m2 for the plasma membrane, a cytoplasmic permittivity of 57 +/- 5.4 and a cytoplasmic conductivity of 0.52 +/- 0.05 S/m. By contrast, parasitized cells exhibited electrorotation spectra with a time-dependency that suggested significant net ion outflux via the plasma membrane and it was not possible to derive reliable cell parameter values in this case. To overcome this problem, cell membrane dielectric properties were instead determined from dielectrophoretic crossover frequency measurements made as a function of the cell suspending medium conductivity. The crossover frequency for normal cells depended linearly on the suspension conductivity above 20 mS/m and analysis according to the single-shelled oblate spheroid dielectric model yielded values of 11.8 mF/m2 and 271 S/m2, respectively, for the specific capacitance and conductance of the plasma membrane. Unexpectedly, the crossover frequency characteristics of parasitized cells at high suspending medium conductivities were non-linear. This effect was analyzed in terms of possible dependencies of the cell membrane capacitance, conductance or shape on the suspension medium conductivity, and we concluded that variations in the membrane conductance were most likely responsible for the observed non-linearity. According to this model, parasitized cells had a specific membrane capacitance of 9 +/- 2 mF/m2 and a specific membrane conductance of 1130 S/m2 that increased with increasing cell suspending medium conductivity. Such conductivity changes in parasitized cells are discussed in terms of previously observed parasite-associated membrane pores. Finally, we conclude that the large differences between the dielectrophoretic crossover characteristics of normal and parasitized cells should allow straightforward sorting of these cell types by dielectrophoretic methods.

Deep-plane cervicofacial flap for reconstruction of large cheek defects

We describe our experience using a deep-plane technique to create an inferiorly based musculocutaneous flap to decrease distal flap necrosis in reconstruction of large anterior cheek and lower eyelid defects. Our early experience with the use of the deep-plane cervicofacial flap has been encouraging. We believe that it deserves more study for use in the population at risk for flap necrosis.

Membrane changes associated with the temperature-sensitive P85gag-mos-dependent transformation of rat kidney cells as determined by dielectrophoresis and electrorotation

Conventional dielectrophoresis (cDEP) and electrorotation (ROT) measurements have been used to determine the dielectric properties of a clone of normal rat kidney cells, designated 6m2, that exhibits a transformed phenotype at 33 degrees C and a non-transformed phenotype at 39 degrees C. cDEP measurements of the crossover frequencies at which individual 6m2 cells experienced zero cDEP force performed as a function of the conductivity of the suspension medium revealed that, in response to a temperature shift from 33 degrees C to 39 degrees C for 24 h, the mean specific cell membrane capacitance and conductance fell significantly (P < 0.01) from 42.3 (+/-1.3) to 30.3 (+/-2.9) mF/m2 and 743 (+/-422) to 567 (+/-326) S/m2, respectively. ROT analyses demonstrated a similar reduction for the membrane capacitance from 37.2 (+/-7.3) to 27.4 (+/-6.1) mF/m2, and also showed that accompanying changes in the mean internal electrical conductivity and dielectric permittivity of the cells were insignificant. Scanning electron microscopy was used to examine the surface morphology of the cells and, in agreement with our previous reports for leukemia cells, the observed membrane capacitance values correlated closely with the morphological complexity of the cell membrane surface. The observed changes in the membrane dielectric properties are discussed in terms of their biological significance and their relationship to previously-detected changes in cell surface charge.

A histological comparison of 50% and 70% glycolic acid peels using solutions with various pHs

BACKGROUND

Seventy percent glycolic acid solutions are being commonly used as superficial chemical peeling agents. The pH of these solutions ranges from 0.08 to 2.75. The histologic effects of these various pH solutions on human skin have not been studied.

OBJECTIVE

The histologic effects of several commercially available glycolic acid solutions at various pHs were examined.

METHODS

Test areas of seven glycolic acid solutions were applied to facial skin of two patients. The skin was not prepped for a peel prior to the application of the acid. The solution was left in place for 30 minutes, then neutralized. After 48 hours, a 2-mm punch biopsy was performed and examined histologically.

RESULTS

The peeling solutions with a pH below 2 demonstrated the potential to induce crusting and necrosis, which was not seen with the partially neutralized solutions with a pH above 2. The higher concentration acids (70%) created more tissue damage than the lower concentration (50%) when comparing solutions with free acid.

CONCLUSION

This study demonstrates that chemical peeling with a 70% free glycolic acid creates more tissue damage than a free glycolic acid. When using a 70% glycolic acid solution, the lower pH products (below pH 2) create more necrosis than the partially neutralized products with a pH above 2. At this time there is no evidence that creating necrosis leads to a more favorable result of the peel. Therefore, the use of partially neutralized glycolic acid solutions seems prudent, since they have a better safety profile than low pH solutions, which contain only free glycolic acid.

Inhibition of human DNA ligase I activity by zinc and cadmium and the fidelity of ligation

Heavy metals, including zinc (Zn) and cadmium (Cd), are potentially important genotoxic agents in our environment. Here we report that human DNA ligase I, the major form of the enzyme in replicative cells, is a target for Zn and Cd ions. ZnCl2 at 0.8 mM caused complete inhibition of DNA ligase I activity, whereas only 0.04 mM CdCl2 was required to achieve a similar effect. Both metals affected all three steps of the reaction, namely, the formation of ligase-AMP intermediate, the transfer of the AMP to DNA and the ligation reaction that succeeds the formation of the AMP-DNA complex. Unlike F-ara-ATP and the natural protein inhibitor of DNA ligase-I, these metals may affect different domains of the enzyme. Moreover, these metal ions did not increase the rate of misligation of F-ara-A-modified DNA or mismatched DNA substrates, but considerable misligation was observed for the T:C mispairing. These data support the notion of high fidelity of the human DNA ligases and that the major action of these metal ions on the enzyme is their inhibitory function.

Electrorotational studies of the cytoplasmic dielectric properties of Friend murine erythroleukaemia cells

Electrorotation (ROT) spectra of Friend murine erythroleukaemia DS19 cells were measured in the frequency range 10 kHz-100 MHz as a function of suspension osmolality and cell differentiation treatment with hexamethylene bisacetamide (HMBA). A minimization program was employed to curve-fit the measured spectra using a single-shell dielectric model, allowing the derivation of cellular interior conductivity and permittivity (valid for the frequency range 10-100 MHz) and the cytoplasmic membrane capacitance (its dependence on the cell differentiation state and suspension osmolality having been reported earlier). Following HMBA treatment, DS19 cells exhibited a slight increment in average interior permittivity and a decrement in interior conductivity, although the changes were not statistically significant. For both untreated and HMBA treated samples, the average interior conductivity increased and permittivity decreased with increasing suspension osmolality. Of significance was that the average permittivity of cell interiors was larger than that of pure water. The electrorotation spectra of freshly prepared cell nuclei were measured, and the derived nuclear dielectric parameters were employed in numerical simulations to investigate the effects of nuclei on the ROT spectra of intact cells. Other cellular internal structures such as mitochondria were also analysed using theoretical simulations. It was concluded that the derived large permittivity values did not result from cell nuclei or mitochondria, and, instead, we suggest that they may arise from the combined effects of several cytoplasmic organelles.

Non-uniform spatial distributions of both the magnitude and phase of AC electric fields determine dielectrophoretic forces

It is well known that the conventional dielectrophoretic force acting on a polarised particle in a non-uniform AC electric field is proportional to the in-phase component of the induced dipole moment and the non-uniformity of the field strength. In contrast, the travelling-wave-dielectrophoretic force that acts on a particle subjected to a travelling electric field is proportional to the out-of-phase component of the induced dipole moment. We derive a theory that unifies the description and interpretation of conventional dielectrophoretic and travelling-wave-dielectrophoretic forces. We show that a particle in a non-uniform AC electric field experiences a dielectrophoretic force due to spatial non-uniformities of the magnitude and the phase of the field interacting, respectively, with the in-phase and out-of-phase components of the induced dipole moment. The theory is used to explain the translational effects observed for particles in the presence of standing, travelling and rotating fields in several experimental electrode configurations. The good agreement found between the experimental observations and the theoretical predictions validate the theory.

Separation of human breast cancer cells from blood by differential dielectric affinity

Electrorotation measurements were used to demonstrate that the dielectric properties of the metastatic human breast cancer cell line MDA231 were significantly different from those of erythrocytes and T lymphocytes. These dielectric differences were exploited to separate the cancer cells from normal blood cells by appropriately balancing the hydrodynamic and dielectrophoretic forces acting on the cells within a dielectric affinity column containing a microelectrode array. The operational criteria for successful particle separation in such a column are analyzed and our findings indicate that the dielectric affinity technique may prove useful in a wide variety of cell separation and characterization applications.

Identification of a brain- and reproductive-organs-specific gene responsive to DNA damage and retinoic acid

We have identified and sequenced a new gene from human cells that is responsive to DNA damage and retinoic acid treatment, and it is highly expressed in brain and reproductive organs (BRE). This BRE gene encodes an mRNA of 1.7-1.9 kb, with an open reading frame of 1,149 bp, and gives rise to a deduced polypeptide of 383 amino acid residues. Treatment of fibroblast cell with UV and 4-nitroquinoline-1-oxide caused more than 90% and 50% decreases in BRE mRNA, respectively. Similar decreases in BRE expression were observed in RA-treatment of the brain glioma cell U-251 and the promyelocytic cell HL-60. Decrease in BRE mRNA was also observed in a squamous carcinoma cell, 1483, that showed X-ray resistance and has a more aggressive tumorigenic phenotype, but BRE expression was unchanged in cells after growth inhibition. These data indicate that BRE is a house-keeping gene and it may play a role in homeostatis or in certain pathways of differentiation in cells of neural, epithelial and germ line origins.

Changes in Friend murine erythroleukaemia cell membranes during induced differentiation determined by electrorotation

We used electrorotation measurements to investigate alterations in the plasma membranes of DS19 murine erythroleukaemia cells that accompanied erythropoietic differentiation induced by hexamethylene bisacetamide (HMBA). Following 3 days of HMBA treatment, the mean cell membrane specific capacitance determined from electrorotation spectra of individual, viable cells at physiological tonicity (300 mosmol/kg) fell from 1.74 to 1.53 microF/cm2, in agreement with trends observed earlier by dielectrophoretic measurements on bulk cell populations. Scanning and transmission electron microscopy revealed that the relatively high values found for cell membrane capacitance (> 1 microF/cm2) reflected the large area of plasma membrane associated with complex surface morphology including numerous microvilli. Furthermore, it demonstrated that the fall in membrane capacitance during HMBA treatment correlated with a reduction in the density of these complex surface features. Differences in the mechanical characteristics of the cell membranes of untreated and treated cells were then examined by exposing cells to osmotic stress. The intricacy of membrane morphology intensified with increasing osmolality of the suspending medium and this was reflected in higher specific capacitance values. When the osmolality was increased from 210 to 450 mosmol/kg, the mean membrane capacitance of untreated DS19 cells changed from 1.58 to 2.05 microF/cm2 while that for HMBA-treated cells changed from 1.47 to 1.72 microF/cm2, a significantly smaller response. This demonstrated that cells exposed to 72 h of differentiation treatment had an enhanced mechanical resilience as compared with their untreated counterparts, evidencing the early stages of the development of the membrane skeleton which becomes fully developed in mature erythrocytes. Our findings demonstrate the value of electrorotation measurements as a method for the non-invasive characterisation of viable leukaemic cells and their responses to stimuli and show that the membrane capacitance values so derived reflect membrane morphology.

The preauricular portion of the rhytidectomy incision

OBJECTIVE

To evaluate the best placement of the preauricular portion of the rhytidectomy incision in the female patient from the aesthetic point of view.

DESIGN

Blind, randomized review of close-up photographs of the ear area in 36 patients after rhytidectomy.

SETTING

Office surgical suite, accredited by Accreditation Association of Ambulatory Health Care.

PARTICIPANTS

Two facial plastic surgeons and two plastic surgeons, all skilled rhytidectomy surgeons.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Participants received close-up photographs of the ear area of 36 patients at least 6 months after rhytidectomy. Eighteen patients had posterior tragal edge incisions and 18 patients had pretragal incisions. Cases were randomized. Participants were asked to rate the preauricular portion of the rhytidectomy incisions overall as to aesthetic results. The categories were excellent, good, average, acceptable, and poor.

RESULTS

Results of surveys were collated. Three categories of results were determined: best, acceptable, and poorest. Posterior tragal edge incisions scored higher than pretragal incisions. Those incisions that scored in the best category tended to have a normal contour of the tragus and normal pretragal sulcus. Incisions that scored in the poorest category tended to have a flat posttragal edge with obliteration of the pretragal sulcus.

CONCLUSIONS

The incision at the posterior edge of the tragus is preferred over the pretragal incision for female rhytidectomy patients except those with a large, prominent or angulated tragus.

Membrane changes accompanying the induced differentiation of Friend murine erythroleukemia cells studied by dielectrophoresis

Dielectrophoresis measurements obtained using an image processing technique are reported over the frequency range 1 Hz to 100 kHz for the Friend murine erythroleukemia cell lines DS19 and R1 before and after treatment with hexamethylene bisacetamide and dimethylsulfoxide, agents that induce terminal differentiation in DS19 but not in R1 cells. Data are analyzed according to the single shell dielectric model of the cell. The membrane capacitance was found to fall by 30% and membrane conductivity by a factor of at least 5 when DS19 cells were induced to differentiate. R1 cells showed no such response. While the theoretical model was found to be useful for comparing differences in data for the different cell lines, several significant discrepancies between its predictions and the experimental data were observed, including positive dielectrophoretic collection at frequencies below 20 Hz and a smaller than predicted response to the membrane permeabilizing agents saponin and valinomycin. Factors that may have accounted for these discrepancies include surface charge effecgs, conduction parallel to the plasma membrane surface, and intracellular compartments.

Biochemical characterization of a protein inhibitor for DNA ligase I from human cells. Regulation/replication/repair/recombination

An inhibitor for DNA ligase I has recently been purified from human cells. This inhibitor of 55-75 kDa forms a reversible complex with DNA ligase I, but has no effect on DNA ligase II and T4 DNA ligase, suggesting that it may play a regulatory role for DNA replication and repair. This report shows that the inhibitor was sensitive to heating at 52 degrees C and to trypsin treatment, indicating that it is a heat-labile protein. The inhibitor affected the ligation of double- and single-strand breaks in natural and synthetic DNA, but had no effect on the formation of the ligase-AMP complex and on the subsequent reaction following the formation of the AMP-DNA complex. These data indicate that the major mechanism of action for the inhibitor is the blocking of the second step of the reaction, in which the AMP moiety is transferred from the ligase-AMP to DNA. The site of interaction for the enzyme is therefore localized in a domain associated with the DNA binding or the AMP-transferring function.

Activation of distinct multidrug-resistance (P-glycoprotein) genes during rat liver regeneration and hepatocarcinogenesis

The multidrug transporter P-glycoproteins are encoded by three multidrug-resistance (mdr) genes in rodents, designated mdr1a (mdr3), mdr1b (mdr1), and mdr2. Only the first two genes are functionally related to multidrug resistance. Activation of rodent mdr genes during liver regeneration and hepatocarcinogenesis has been reported. In mice, mdr1a is activated in hepatocellular carcinomas (HCCs) produced by various carcinogenic protocols, whereas both mdr1a and mdr2 are activated during liver regeneration. In this communication, we report isolating three gene-specific probes for the rat mdr homologues, which were used as probes in an RNase protection assay to demonstrate that mdr1b mRNA was expressed in HCCs induced by two different protocols. Furthermore, high levels of hepatic mdr1b mRNA but only moderate levels of mdr1a and mdr2 mRNA were seen in preneoplastic lesions in rats treated with 2-acetylaminofluorene. Likewise, highly elevated levels of hepatic mdr1b mRNA but only moderately increased levels of mdr1a and mdr2 mRNA were seen after partial hepatectomy. Nevertheless, the general patterns of tissue-specific expression of these three mdr genes were similar in rats and mice. These results reveal a complex hepatic gene expression pattern during hepatocarcinogenesis and hepatic proliferation for this conserved gene family in rodents.

Alterations in expression and structure of the DNA repair gene XRCC1

The repair-associated gene XRCC1 was previously cloned by complementing the hamster mutant EM9, which has a high rate of spontaneous SCE and hypersensitivity to DNA damaging agents. In analyzing XRCC1 gene expression, similar levels of steady-state mRNA were found in normal cells, Bloom's syndrome cells with altered SCE, and in squamous carcinoma cells with differential X-ray sensitivity. An EcoRI restriction fragment-length polymorphism previously identified in XRCC1 did not correlate with the repair phenotypes of these cells. The mRNA of XRCC1 decreased to 20-40% after treatment of cells with a DNA damaging agent. XRCC1 also showed tissue specific expression in rats. The mRNA levels were high in testis (7-8 fold), ovary (3-4 fold) and brain (4-5 fold), when compared with those in intestine, liver and spleen (1-2 fold). These data and the high levels of XRCC1 protein detected in testis indicate that XRCC1 may play an important role in DNA processing during meiogenesis and recombination in germ cells.

New retractor for open rhinoplasty

One of the problems often encountered in external rhinoplasty is retraction of the flap. When a wide, double-pronged retractor is used, the tongue of the external rhinoplasty flap falls between the two points, often obscuring the view of the tip-and-dome anatomy. When vein retractor-type instruments are used, they will often slip and do not stay stable. A retractor has been designed for external rhinoplasty that consists of a wide, double-pronged element to elevate the soft tissues of the lower third of the nose above the cartilaginous and bony anatomy, combined with a central, slightly set-back retractor that holds the tongue of the rhinoplasty flap in a secure, retracted position. This has been a significant improvement in retraction for the external rhinoplasty flap.

Identification of a specific inhibitor for DNA ligase I in human cells

A protein inhibitor for human DNA ligase I has recently been identified. It was copurified with a fraction of the enzymes from HeLa cells through several steps of chromatography. The inhibitor was first identified by the absence of ligation activity of the associated enzyme, while it retained the ability to form the ligase-[32P]AMP adducts. The inhibitor was eluted as a single peak at approximately 0.25-0.30 M NaCl from a Mono S column. It inhibited the ligation of both double-stranded and single-stranded breaks by purified DNA ligase I but not by T4 DNA ligase and DNA ligase II. Subsequent gel-filtration chromatography indicated that this inhibitor, with a molecular mass of 55-75 kDa, could form a complex with DNA ligase I and inhibited the DNA ligation activity. Rechromatography of the ligase I-inhibitor complex in high-salt conditions resulted in the dissociation of the complex and the restoration of enzyme activity, indicating that the physical interaction of inhibitor with DNA ligase I is one of the mechanisms of inhibition. These data indicate that this protein inhibitor for DNA ligase I may play a specific role in regulating DNA ligation during replication, repair, or recombination.

Dual mode of inhibition of purified DNA ligase I from human cells by 9-beta-D-arabinofuranosyl-2-fluoroadenine triphosphate

9-beta-D-Arabinofuranosyl-2-fluoroadenine (F-ara-A) is an analogue of adenosine and deoxyadenosine with potent anti-tumor activity. The mechanism of action for this compound has been elucidated as the inhibition of DNA and RNA synthesis, induction of DNA fragmentation, and genetic damage. This study demonstrated that DNA ligase I, an enzyme involved in DNA replication, is a target for the drug action. F-ara-adenine triphosphate (F-ara-ATP) at 80 microM inhibited the activity of DNA ligase I by more than 90%. In contrast, eight other related nucleoside analogues showed no effect on the enzyme activity at 200 microM. F-ara-ATP inhibited DNA ligation in two distinct ways. First, F-ara-ATP directly interacted with DNA ligase I and inhibited the formation of the ligase-AMP complex. This inhibition could not be reversed when free F-ara-ATP was eliminated from the treated enzyme; however, the addition of pyrophosphate, followed by gel filtration chromatography, restored enzyme activity, indicating that F-ara-ATP bound to the enzyme and altered the AMP-binding site. Secondly, the activity of DNA ligase I was inhibited when F-ara-ATP was incorporated into the 3' terminus of the DNA substrate. The dual mode of inhibition of DNA ligase I by F-ara-ATP indicates that its effect on DNA ligation may be important in the inhibition of DNA synthesis and the cytotoxicity of F-ara-A.

IL-2-dependent murine T-cell lines and clones expressing gamma/delta T-cell antigen receptors. I. Functional and biochemical characterization

We have developed two stable IL-2-dependent T-cell lines designated AKV-I and AKV-N from the enlarged spleens, respectively, of an AKV1 and an NFS mouse. Immunofluorescence staining with the appropriate monoclonal antibodies revealed that cells of the AKV-I cell line were alpha beta TCR-CD3+CD4-CD5-CD8+CD25+, whereas cells of the AKV-N cell line were alpha beta TCR-CD3+CD4-CD5+CD8-CD25+. A number of T-cell clones were developed from the AKV-I or AKV-N T-cell lines by limiting dilution and analysed by immunofluorescence. All clones tested were alpha beta TCR-CD3+CD4-CD25+. Certain T-cell clones expressed the CD5 antigen, whereas others expressed the CD8 antigen. The AKV-I cell line responded by proliferation to rIL2, rIL4, phorbol myristate acetate (PMA), PMA plus IL-4 and PMA plus PHA or Con A. In contrast, the AKV-N cell line did not respond to rIL-4 or rIL-4 plus PMA and exhibited only a modest proliferative response to PMA alone. Both AKV-I and AKV-N T-cell lines as well as a large number of T-cell clones examined were able to lyse cells of the PU5-IR murine cell line in the presence of the anti-CD3 (clone 145-2C11) MoAb, demonstrating their ability to mediate cytotoxicity in this system. Biochemical analysis of both AKV lines and a number of clones by immunoprecipitation with the anti-CD3 MoAb, followed by one-dimensional (either non-reducing or reducing) or two-dimensional (non-reducing/reducing) SDS-PAGE, revealed that the AKV lines and clones expressed a disulphide-linked dimer. Under non-reducing conditions, a band in the range of 75-85 kDa was observed and upon reduction it was resolved into two discrete polypeptide chains of 43-44 kDa and 48 kDa in certain AKV-I cells or 38 kDa and 42 kDa in certain AKV-N cells. In other T-cell clones or lines a broad band of 42-47 kDa was observed in AKV-I cells or 38-45 kDa in AKV-N cells. These results suggest the presence of different forms of disulphide-linked dimers on these cells. Northern blotting analysis using probes specific for the constant regions of the alpha-, beta-, gamma- and delta-chains of the T-cell antigen receptor revealed that all the AKV cell lines or clones tested expressed full-length alpha-, gamma- and delta-chain mRNA, whereas beta-chain mRNA was absent.(ABSTRACT TRUNCATED AT 250 WORDS)

Specific reduction of I-compound levels in DNA from spontaneous hepatomas of 22-24 month old male C3H mice

As previously shown by 32P-postlabeling, I-compound levels are reduced in target tissue DNA of animals exposed to one of several non-genotoxic hepatocarcinogens, e.g. 2,3,7,8-tetrachlorodibenzo-p-dioxin, carbon tetrachloride, peroxisome proliferators and choline-devoid diet. I-compound levels are further reduced, sometimes to undetectable levels, in chemically induced, transplantable rat (Morris) hepatomas and hepatocellular carcinomas induced by peroxisome proliferators or choline-devoid diet. The current study investigated I-compounds in spontaneous hepatic adenomas of genetically susceptible male C3H mice. DNA samples from individual tumors, background livers (non-tumor bearing lobe from tumor bearing mouse) and non-tumor bearing normal livers taken from 22-24 month old animals were analyzed by 32P-postlabeling. I-compound profiles were qualitatively comparable among the three types of tissues. However, levels of most I-compounds were 2.6-5.0 times lower in tumors than in background liver and non-tumor bearing normal liver. There were virtually no differences between background liver and normal liver. Taken together with the previously reported I-compound deficiency in carcinogen-induced hepatomas, the present observations on genetically initiated neoplasms suggest that this phenomenon may play a role in hepatocarcinogenesis and maintenance of neoplasia.

Suppression of in vitro chemical transformation by the carcinogenesis-promoting, viable yellow gene Avy

The presence of the viable yellow Avy and lethal yellow Ay genes has been demonstrated to accelerate the process of tumorigenesis in mice bearing genetically, chemically or virally initiated cells. This promoting effect has been reported in the liver, lung, breast, bladder and skin. Although it has been demonstrated that the accelerated process is associated with systemic, pathophysiologic alterations such as an alteration in the lipogenic pathway, which in turn leads to obesity, alteration in glucose metabolism and/or random immunologic alterations, no examination of the in vitro 'tumorigenic' susceptibility of the cells of animals bearing the yellow genes has yet been reported. In the current study, spontaneous and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced transformation was determined in skin-derived fibroblasts from C57BL/6N-Avy/a mice (Hy) and their black a/a litter mates (B1-). The growth rate of untreated fibroblasts was greater for those from the yellow mice than from the black, while susceptibility to MNNG toxicity was equivalent. However, the rate of spontaneous and chemically induced transformation was consistently and significantly higher in the cells obtained from the black a/a mice than in those from yellow, Avy/a litter mates. These findings, with others from the literature, suggest that the Avy gene may suppress transformation and carcinogenic susceptibility in specific cells, such as fibroblasts, while the systemic effects of the gene are promotional in other cells.

Expression of specific UDP-glucuronosyltransferase isoforms in carcinogen-induced preneoplastic rat liver nodules

The expression of specific UDP-glucuronosyltransferase isoforms in 2-acetylaminofluorane-induced rat liver preneoplastic nodules was studied; livers from pair-fed littermates were used as controls. For comparison, liver and kidney from 3-methylcholanthrene-treated or untreated (control) rats were used. Steady-state UDP-glucuronosyltransferase mRNA levels were determined by Northern blot analysis or in situ hybridization of tissue sections using a 30-mer oligonucleotide specific for the 3-methylcholanthrene-inducible UDP-glucuronosyltransferase (which is active toward 4-nitrophenol) or a double-stranded cDNA probe specific for androsterone-UDP-glucuronosyltransferase. For 3-methylcholanthrene-inducible UDP-glucuronosyltransferase, the mRNA level was very low in control liver; there was a 15-fold increase after 3-methylcholanthrene treatment. This mRNA was present at relatively high concentration in the kidney and there was a threefold increase after 3-methylcholanthrene administration. In livers with preneoplastic nodules 1 mo after cessation of carcinogen administration, this mRNA concentration was approximately 15 times greater than in control liver. Similar changes in the level of the 3-methylcholanthrene-inducible UDP-glucuronosyltransferase were also observed by in situ hybridization of tissue sections. Immunocytochemical studies using an antiserum that recognizes the 3-methylcholanthrene-inducible UDP-glucuronosyltransferase showed a marked increase in the concentration of this isoform in preneoplastic nodules compared with the adjacent nonnodular liver.

Overexpression of the multidrug resistance gene mdr3 in spontaneous and chemically induced mouse hepatocellular carcinomas

Overexpression of a family of plasma membrane glycoproteins, known as P-glycoproteins, is commonly associated with multidrug resistance in animal cells. In rodents, three multidrug resistance (mdr or pgp) genes have been identified, but only two can confer the multidrug resistance phenotype upon transfection into animal cells. Using the RNase protection method, we demonstrated that the levels of three mdr gene transcripts differ among mouse tissues, confirming a previous report that the expression of these genes is tissue specific (J.M. Croop, M. Raymond, D. Huber, A. DeVault, R. J. Arceci, P. Gros, and D. E. Housman, Mol. Cell. Biol. 9:1346-1350, 1989). The levels of mdr transcripts were determined for mouse liver tumors spontaneously arising in both C3H/HeN and transgenic animals containing the hepatitis B virus envelope gene and for tumors induced by two different carcinogenic regimens in C57BL/6N and B6C3-F1 mice. The mdr3 gene was overexpressed in all 22 tumors tested. Our results demonstrate that overexpression of the mdr3 gene in mouse liver tumors does not require exposure of the animals to carcinogenic agents and suggest that its overexpression is associated with a general pathway of hepatic tumor development. The overexpression of the mdr3 gene, which is the homolog of human mdr1 gene, in hepatocellular carcinomas may be responsible for the poor response of these tumors to cancer chemotherapeutic agents.

Fingerprinting of near-homogeneous DNA ligase I and II from human cells. Similarity of their AMP-binding domains

DNA ligases play obligatory roles during replication, repair, and recombination. Multiple forms of DNA ligase have been reported in mammalian cells including DNA ligase I, the high molecular mass species which functions during replication, and DNA ligase II, the low molecular mass species which is associated with repair. In addition, alterations in DNA ligase activities have been reported in acute lymphocytic leukemia cells, Bloom's syndrome cells, and cells undergoing differentiation and development. To better distinguish the biochemical and molecular properties of the various DNA ligases from human cells, we have developed a method of purifying multiple species of DNA ligase from HeLa cells by chromatography through DEAE-Bio-Gel, CM-Bio-Gel, hydroxylapatite, Sephacryl S-300, Mono P, and DNA-cellulose. DNA-cellulose chromatography of the partially purified enzymes resolved multiple species of DNA ligase after labeling the enzyme with [alpha-32P]ATP to form the ligase-[32P]AMP adduct. The early eluting enzyme activity (0.25 M NaCl) contained a major 67-kDa-labeled protein, while the late eluting activity (0.48 M NaCl) contained two major labeled proteins of 90 and 78 kDa. Neutralization experiments with antiligase I antibodies indicated that the early and late eluting activity peaks were DNA ligase II and I, respectively. The three major ligase-[32P]AMP polypeptides (90, 78, and 67 kDa) were subsequently purified to near homogeneity by elution from preparative sodium dodecyl sulfate-polyacrylamide gels. All three polypeptides retained DNA ligase activities after gel elution and renaturation. To further reveal the relationship between these enzymes, partial digestion by V8-protease was performed. All three purified polypeptides gave rise to a common 22-kDa-labeled fragment for their AMP-binding domains, indicating that the catalytic sites of ligase I and II are quite similar, if not identical. Similar findings were obtained from the two-dimensional gel electrophoresis of their AMP-binding domains in the trypsin-digested protein fragments. The results also suggested that these isozymes have been derived from the same primordial DNA sequence or from the same precursor protein. The purification scheme and the data obtained will be instrumental for the further elucidation of the biological roles of various DNA ligases from human cells.

Role of the AKR gene locus AKv-1 in susceptibility to chemical induction of thymic lymphomas

Various strains of mice demonstrate widely differing susceptibility to chemical induction of thymic lymphomas, in both timing and incidence. In AKR mice tumors appear very early and at high incidence after a single dose of N-methyl-N-nitrosourea, while in other strains they appear later and at lower incidences. In an attempt to determine the potential role of AKR ecotropic murine leukemia virus loci in this process, congenic mice of NFS/N background, into which the highly productive ecotropic murine leukemia virus loci AKv-1 or AKv-2 has been transferred, were challenged with N-methyl-N-nitrosourea. Although they had a lower incidence of thymic lymphomas than did the parental donor AKR, the NS.AKv-1 mice had a tumor incidence twice that of NFS/N or NS.AKv-2. However, no difference in timing was noted, and these three strains demonstrated tumor appearance much later than that of AKR/N. It is suggested that the presence of the AKv-1 loci, or a gene of the closely associated genomic region, increases the number of target cells that are susceptible to N-methyl-N-nitrosourea.

Submental W-plasty for correction of 'turkey gobbler' deformities

There are many causes and types of submental contour deformities. One such deformity called a turkey gobbler, is caused by an excess of flaccid submental skin and as an isolated defect is seen more commonly in men. We have found that skin excision and a running submental W-plasty for correction of this deformity yields a superior cosmetic result with excellent camouflage of the submental scar. Two cases are illustrated.

External approach to rhinoplasty

The external approach to rhinoplasty offers several distinct advantages over the classical endonasal approach for incising, excising, repositioning, and augmenting the framework of the nose for functional and aesthetic improvement. The history of external rhinoplasty, advantages and alleged disadvantages are discussed; personal experience since 1982 is outlined. Various nasal deformities which have been corrected using the external approach are listed and several are discussed and illustrated. This report presents an overview of the technique of external rhinoplasty which will become even more popular as the advantages continue to be recognized by more nasal surgeons.

Dielectrophoretic characterisation of Friend murine erythroleukaemic cells as a measure of induced differentiation

Dielectrophoresis measurements, the study of the motion of particles in non-uniform a.c. electrical fields, have been made on three cell lines (DS19, R1 and DR1) of Friend murine erythroleukaemia cells as a function of hexamethylene bisacetamide (HMBA) treatment. The effects of saponin treatment on R1 cells and neuraminidase on human red blood cells were also studied. It is shown that the dielectrophoretic behaviour can be interpreted in terms of cell surface charge and cell membrane conductivity effects. HMBA reduces the cell surface charge on all three cell lines, and in lines DS19 and DR10, where the cells are induced to differentiate, there is an increase in effective cell conductivity. This gain in conductivity is concluded to be associated with either an enhanced lateral electrophoretic motion of delocalised ions or of the polarisability of dipoles at the membrane surface.

Heme synthesis in normal mouse liver and mouse liver tumors

Hepatic cancers from mice and rats demonstrate decreased levels of delta-aminolevulinic acid synthase, the rate-limiting enzyme in the heme synthetic pathway, and increased heme oxygenase, the heme-catabolizing enzyme. These findings suggest that diminution of P-450, b5, and catalase in these lesions may result from a heme supply that is limited by decreased heme synthesis and increased heme catabolism. Heme synthesis was measured in mouse liver tumors (MLT) and adjacent tumor-free lobes (BKG) by administering the radiolabeled heme precursors 55FeCl3 and [2-14C]glycine and subsequently extracting the heme for determination of specific activity. Despite reduced delta-aminolevulinic acid synthase activity in MLT, both tissues incorporated [2-14C]glycine into heme at similar rates. At early time points, heme extracted from MLT contained less 55Fe than that from BKG. This was attributed to the findings that MLT took up 55Fe at a slower rate than BKG and had larger iron stores than BKG. The amount of heme per milligram of protein was also similar in both tissues. These findings militate against the hypothesis that diminished hemoprotein levels in MLT result from limited availability of heme. It is probable, therefore, that decreased hemoprotein levels in hepatic tumors are linked to a general program of dedifferentiation associated with the cancer phenotype. Diminution of hemoprotein in MLT may result in a relatively increased intracellular heme pool. delta-Aminolevulinic acid synthase and heme oxygenase are, respectively, negatively and positively regulated by heme. Thus, their alteration in MLT may be due to the regulatory influences of the heme pool.

Alterations in electrophoretic mobility, diaphorase activity, and terminal differentiation induced in murine erythroleukemia lines by differentiating agents

The electrophoretic mobilities (EPMs) and semiquinone reductase activities of two clones of Friend murine erythroleukemia (MEL) cells were investigated as a function of treatment with the inducing agents dimethylsulfoxide (DMSO) and hexamethylene bisacetamide (HMBA). As reported previously by others, the inducible clone DS19 lost its ability to grow in soft agar and expressed hemoglobin as judged by benzidine/H2O2 staining after 96 hours of treatment with 1% DMSO or 4 mM HMBA. In addition, its EPM fell by 14%, its semiquinone reductase activity by 40%, and its mean diameter by 10%. The second clone, R1, retained its ability to grow in soft agar and lacked hemoglobin expression after treatment with HMBA and DMSO, characterizing it as noninducible. However, R1 did demonstrate alterations in EPM, semiquinone reductase activity, and cell diameter that closely paralleled those found in DS19. Such responses were not seen in three non-MEL cell lines exposed to HMBA or DMSO, suggesting that clone R1 responded to these inducing agents in a cell-line specific manner but that its ability to complete the sequences necessary for differentiation may be blocked at an unknown point distal to the block characteristic of untreated cells. The data show that while a reduction in EPM, semiquinone reductase activity, and cell diameter accompany induced differentiation in MEL cells, such changes can occur in the absence of a commitment to terminal differentiation.

[Reducing chloramines in drinking water]

Monochloramine is produced when drinking water containing ammonium is chlorinated. It has long been known that activated charcoal destroys monochloramine. However, exact data for the dimensioning of a dechloramination plant were lacking. Four different commercially available activated charcoals were characterized (size of particle, iodine number) and examined for their effectiveness in removing monochloramines. The degradation of monochloramine by active charcoal is based on a chemical reaction of first order between carbon and monochloramine. The types of activated charcoal considerably differ in terms of reaction velocity, due in part to the mean granular size. The final concentration of the monochloramines is influenced only by their length of stay in the activated carbon filter, the temperature and the inflow concentration. A mathematical model describes the dependence of the degradation rate of the monochloramines on various factors. With its aid a nomogram can be established with which, simply and quickly, the activated charcoal needed in a concrete case can be determined.