Continuous Exposure Experiments Research Articles

A Noninvasive Quantitative Method for Evaluating Intestinal Exposure to Microplastics Based on the Excretion and Metabolism Patterns of Microplastics and Their Additives.

Microplastics (MPs) pose potential health risks to the intestinal tract and gut microbiota, a topic that has garnered significant attention. However, the absence of quantitative assessment methods for human gut MP exposure impedes related health risk assessments. Here, we performed long-term continuous exposure experiments on mice using MPs that mimic actual human exposure characteristics. The daily excretion of fecal MPs and the concentrations of phthalates (PAEs) and their metabolites (mPAEs) in serum and urine were detected. The cumulative excretion rate of fecal MPs remains stable at about 93%. A significant linear correlation was observed between MP exposure and concentration of mPAEs in urine for both low MP (LMP; 150 μg of MPs/d) (R2 = 0.90) and high MP (HMP; 360 μg of MPs/d) groups (R2 = 0.97). Moreover, a strong correlation was found between daily PAEs exposure and total MP-associated PAEs exposure in both LMP (R2 = 0.77) and HMP (R2 = 0.88) groups. Based on these findings, we established a noninvasive model and evaluated multiple MP exposure parameters in the human gut across 6 continents, 30 countries, and 133 individuals. This study offers novel insights for the quantitative assessment of in vivo MP exposure and provides technical support for assessing the health risks of MPs.

Enantioselective bioaccumulation and toxicological effects of chiral neonicotinoid sulfoxaflor in rats

Sulfoxaflor is a widely used fourth-generation neonicotinoid pesticide, which has been detected in biological and environmental samples. Sulfoxaflor can potentially be exposed to humans via the food chain, thus understanding its toxic effects and enantioselective bioaccumulation is crucial. In this study, toxicokinetics, bioaccumulation, tissue distribution and enantiomeric profiles of sulfoxaflor in rats were investigated through single oral exposure and 28-days continuous exposure experiment. Sulfoxaflor mainly accumulated in liver and kidney, and the (−)-2R,3R-sulfoxaflor and (−)-2S,3R-sulfoxaflor had higher enrichment than their enantiomers in rats. The toxicological effects were evaluated after 28-days exposure. Slight inflammation in liver and kidney were observed by histopathology. Sphingolipid, amino acid, and vitamin B6 metabolism pathways were significantly disturbed in metabonomics analysis. These toxicities were in compliance with dose-dependent effects. These results improve understanding of enantioselective bioaccumulation and the potential health risk of sulfoxaflor.

Bacterial community succession and the enrichment of antibiotic resistance genes on microplastics in an oyster farm

Microplastics can be colonized by microorganisms and form plastisphere. However, knowledge of bacterial community succession and the enrichment of antibiotic resistance genes (ARGs) and pathogens on microplastics in aquaculture environments is limited. Here, we conducted a 30-day continuous exposure experiment at an oyster farm. Results showed that the alpha-diversity of communities on most microplastics continuously increased and was higher than in planktonic communities after 14 days. Microplastics could selectively enrich certain bacteria from water which can live a sessile lifestyle and promote colonization by other bacteria. The composition and function of plastisphere communities were distinct from those in the surrounding water and influenced by polymer type and exposure time. Microplastics can enrich ARGs (sul1, qnrS and blaTEM) and harbor potential pathogens (e.g., Pseudomonas aeruginosa). Therefore, microplastic pollution may pose a critical threat to aquaculture ecosystems and human health. Our study provides further insight into the ecological risks of microplastics.

Polyethylene microplastics increases the tissue damage caused by 4-nonylphenol in the common carp (Cyprinus carpio) juvenile

Plastic particles have the ability to transfer harmful chemical pollutants due to their high adsorption capacity. Therefore, this study aimed to investigate the effects of combined exposure to polyethylene microplastics (PE-MPs) and 4-nonylphenol (4-NP) on juvenile common carp (Cyprinus carpio) using histopathological and histochemical biomarkers. Fish were separated into a control group and three treatment groups (10 mg/L PE-MPs; 10 mg/L PE-MPs + 200 µg/L 4-NP; 200 µg/L 4-NP) for a two-week continuous exposure experiment followed by two weeks of recovery. The three treatment groups showed histopathological changes compared to the control. These alterations included severe edema, lifting of the outer epithelium, interlamellar fusion and vacuolation, secondary lamellar shortening and complete fusion, increased mucous cell numbers in the gill tissue, enlargement of inner layer stratum periventricular, cell degeneration with pyknotic nuclei, increased blood capillaries, spongiosis in the brain tissue (optic tectum), central vein hemorrhage, shrunken and fatty degeneration of hepatocytes, rosette shapes around small congested blood sinusoids, vacuoles, necrosis, and severe glycogen reduction in the liver tissue. Some tissue changes improved during the two-week recovery period but did not return to normal. In conclusion, the mixture exposure of the PE-MPs and 4-NP on fish carp induced some histological alterations in most studied tissues and post-exposure made improvement in cellular and tissue structure.

A Near-infrared Persistent Luminescence Imaging Technique for Tracking Nanoparticles in Zebrafish (Danio rerio).

The development of nanotechnology has drawn increased attention to the risks of nanoparticles (NPs). In this work, the near-infrared persistent luminescence imaging technique was used to track the biodistribution of NPs in vivo in zebrafish. Zebrafish were used as a vertebrate animal model to show NPs distribution and the effects of exposure. ZnGa2O4:Cr (ZGOC) was chosen as the probe in this work. In continuous exposure experiments, the results showed more particles accumulated in the intestines than in the gills in both groups. In both the gills and abdomen, the NPs contents were greater in the ZGOC-NH2-treated groups than in the ZGOC groups, and the NPs caused damage to the gills and intestines. Removal exposure experiments indicated that ZGOC and ZGOC-NH2 could be excreted from the body. The metabolism, excretion of NPs, the quantification and monitoring of NPs behavior in biological systems should be examined in further studies.

The effects of continuous Cu(II) exposure compared with a shock dosage of Cu(II) on pollutant removal in activated sludge

In order to determine how Cu(II) exposure affects activated sludge, we investigated pollutant removal and recovery of removal efficiency after continuous exposure to Cu(II) or a shock dosage of Cu(II) in a sequencing batch reactor (SBR) system. The continuous exposure experiment, involving 20 mg L−1 Cu(II), showed that the removal efficiency for chemical oxygen demand (COD) initially decreased rapidly to 7%, but conspicuously recovered to 78% by the 50th day and then dropped to nearly zero by the 160th day. The removal of NH3-N was even more conspicuously inhibited and failed to recover during the experimental period. The continuous dosage of activated sludge with 20 mg L−1 of Cu(II) for nearly 160 d rendered the SBR almost completely unable to remove pollutants. In the shock dosage (batch) experiment, the removal of both COD and NH3-N was inhibited after shock dosages of 10, 20, and 40 mg L−1 Cu(II). However, after 24 h, the removal efficiency of COD at each shock dosage recovered to 81, 60, and 52%, respectively; NH3-N removal efficiency recovered to 78, 74, and 45%, respectively.

Mulch Preferences of the Asian Cockroach (Dictyoptera: Blattellidae)

Mulch preferences of the Asian cockroach, Blattella asahinai Mizukubo, were determined in a series of laboratory experiments. Because this species is a peridomestic pest, mulch preferences may be a key part of an integrated pest management program for homeowners. Five mulches were used: cypress, oak leaf litter, pine straw, rubber, and topsoil. Large arena experiments showed that adult male Asian cockroaches preferred oak leaf litter and pine straw, while adult females preferred oak leaf litter and rubber mulches. Nymphal stages preferred rubber (48.3-62.5% for small and medium instars, respectively) to all other mulches. All stages of the Asian cockroach showed very little preference to topsoil (0%) and cypress mulch (6.3%). Ebeling choice box tests confirmed lack of preference or repellency of adult males to topsoil (17.8 +/- 3.6%) and rubber mulch (15.7 +/- 3.6%). Continuous exposure experiments indicated that pine straw was significantly more toxic to adult males than other mulches (66.7 +/- 18.4% mortality at 7 d). Mulch preferences of the Asian cockroach may be mediated by characteristics of the interstitial spaces in the different mulches. Rubber mulch afforded smaller, more humid spaces that were inaccessible to adults. Because cypress mulch was least preferred by nymphs and adults, use of cypress mulch in an integrated pest management program around homes may help to reduce Asian cockroach populations and limit insecticide exposure to humans, animals, and the environment.

EFFECTS OF DIAZINON ON LARVAE OF THE ASIAN COMMON TOAD (BUFO MELANOSTICTUS, SCHNEIDER 1799)

Continuous subchronic exposure experiments were conducted to assess the effects of diazinon, an organophosphate pesticide, on the survival, growth and activity of larvae of the Asian common toad Bufo melanostictus. Two larval stages, the gill stage (Gosner stages 21 and 22) and gill-atrophy stage (Gosner stages 24 and 25), were continuously exposed to 4 microg/L, 400 mirog/L, and 10 mg/L of commercial-grade diazinon for 30 d. Treatments and untreated controls were maintained in triplicate with water changed and pesticide concentrations renewed every 3 d. Observations showed that subchronic exposure to 400 microg/L and 10 mg/L diazinon caused a significant dose-dependent increase in mortality compared to the control, regardless of the age at which larvae were exposed. One hundred percent mortality was observed in larvae exposed to 10 mg/L. No clear age-related sensitivity was evident in this study. The lethal concentrations at which 50% of the tadpoles (LC50) died during 30 d of continuous exposure were 6 and 7.5 mg/L for gill stage and gill-atrophy stage larvae, respectively. Diazinon impaired larval growth and activity. Tail abnormalities were apparent in larvae exposed to 400 microg/L and 10 mg/L of diazinon. This investigation provides the first empirical evidence of the negative effects of diazinon on the survival, growth and activity of B. melanostictus. The high degree of diazinon toxicity in this study highlights the need to consider important nontarget groups when recommending safe levels of pesticide application.

Effects of insecticide exposure on feeding inhibition in mayflies and oligochaetes

The present study examined the effects of pulse exposures of the insecticide imidacloprid on the mayfly, Epeorus longinmanus Eaton (Family Heptageniidae), and on an aquatic oligochaete, Lumbriculus variegatus Miller (Family Lumbriculidae). Pulse exposures of imidacloprid are particularly relevant for examination, because this insecticide is relatively soluble (510 mg/L) and is most likely to be at effect concentrations during runoff events. Experiments examined the recovery of organisms after a 24-h pulse exposure to imidacloprid over an environmentally realistic range of concentrations (0, 0.1, 0.5, 1, 5, and 10 microg/L). Effects on feeding were measured by quantifying the algal biomass consumed by mayflies or foodstuffs egested by oligochaetes. Imidacloprid was highly toxic, with low 24-h median lethal concentrations (LC50s) in early mayfly instars (24-h LC50, 2.1 +/- 0.8 microg/L) and larger, later mayfly instars (24-h LC50, 2.1 +/- 0.5 microg/L; 96-h LC50, 0.65 +/- 0.15 microg/L). Short (24-h) pulses of imidacloprid in excess of 1 microg/L caused feeding inhibition, whereas recovery (4 d) varied, depending on the number of days after contaminant exposure. In contrast to mayflies, oligochaetes were relatively insensitive to imidacloprid during the short (24-h) pulse; however, immobility of oligochaetes was observed during a 4-d, continuous-exposure experiment, with 96-h median effective concentrations of 6.2 +/- 1.4 microg/L. Overall, imidacloprid reduced the survivorship, feeding, and egestion of mayflies and oligochaetes at concentrations greater than 0.5 but less than 10 microg/L. Inhibited feeding and egestion indicate physiological and behavioral responses to this insecticide.

Repellency and toxicity of mint oil granules to red imported fire ants (Hymenoptera: Formicidae).

Repellency and toxicity of 2% mint oil granules were evaluated against worker red imported fire ants. Solenopsis invicta Buren, in a series of laboratory and field experiments. In continuous exposure experiments, LT50 values ranged from 1.2 h with 164.8 mg/cm2 of 2% mint oil granules to 15.3 h with 1.65 mg/cm2 of granules. LT50 values declined exponentially with increasing rate of mint oil granules. Limited exposure to 164.8 mg/cm2 mint oil granules resulted in > 50% knock down (KD) after 30 min; however, there was no KD at 15 min. Twenty-four hour mortality increased linearly with increasing exposure time. Mean repellency of worker red imported fire ants ranged from 49.2 +/- 5.4% for 0 mg/cm2 (untreated control) of mint oil granules at 30 min to 100% for 147.8 mg/cm2 of mint oil granules at 3 h. Repellency increased with increasing milligrams per square centimeter of mint oil granules and exposure time. In field tests, 100% of mounds opened and treated with mint oil granules were abandoned 5 d after treatment and ants had relocated or formed satellite mounds by 2 d after treatment. Unopened mounds treated topically with mint oil granules were not abandoned, but ants formed satellite mounds 2 d after treatment. Mint oil granules could provide another tool for red imported fire ant integrated pest management, particularly in situations in which conventional insecticides would be inappropriate.

A simulation study of methods for constructing confidence intervals for bioaccumulation factors

Toxicokinetics describe the time course of xenobiotics in an exposed organism. The steady state concentration of the xenobiotic is a characteristic of frequent concern, often summarized in terms of bioaccumulation factors (BAFs). Two experimental protocols are commonly used when estimating BAFs: a continuous exposure experiment and a start-stop exposure experiment. Nonlinear regression is then used for estimating components of the BAF. A variety of methods are available for constructing confidence intervals (CI) for the BAF, including the delta method and Fieller's method. The properties of these CI methods are explored through a simulation study. In particular, the coverage properties of the two CI methods along with their interval widths are examined for a variety of time-course patterns, error distributions, experimental protocols, and sampling designs. Fieller's method is observed to exceed nominal coverage probabilities for all conditions considered (the coverage probability being the probability that a confidence interval contains a parameter it estimates over repeated experiments). The delta method exhibited observed coverage probabilities lower than nominally specified for a number of conditions. For sampling designs in which more of the sampling times are prior to steady state or the stop exposure time, the delta method is observed to provide nominal coverage probabilities with interval widths much narrower than observed with the Fieller's method. Thus, the delta method is preferable when the above sampling time condition is met; however, in all other cases, Fieller's method should be used.

In vitro cytotoxic effect of N-(phosphonacetyl)-L-aspartic acid in liposome against C-26 murine colon carcinoma.

We have investigated the in vitro cytotoxic effect of liposome-encapsulated N-(phosphonacetyl)-L-aspartic acid (PALA) against C-26 murine colon cancer cells, and have compared it in this regard to free PALA. Three different PALA-containing liposomal formulations using distearoylphosphatidylcholine (DSPC), distearoylphosphatidylglycerol (DSPG), and polyethyleneglycol-derivatized distearoylphosphatidylethanolamine (PEG-DSPE) were made and their cytotoxicity was measured. In 72 hr continuous exposure experiment with C-26 cells, the 50% growth inhibitory concentration (IC50) of DSPG-PALA liposome formulation was 0.09 microM, which showed about 65-fold more potent than unencapsulated free PALA (5.1 microM). Similar degree of increase in cytotoxicity was also observed in 1 hr exposure experiment. However, the IC50 of PEG-DSPE-PALA liposome and DSPC-PALA liposome were 10.7 microM and 11.8 microM, respectively, which showed slightly less potent than unencapsulated free PALA. Physical characteristics of PALA-liposomes, such as the size and drug:lipid ratio were also determined. In conclusion, negatively-charged DSPG-PALA liposome showed the highest cytotoxic effect among tested on the C-26 cells in vitro.

Water Loss and Desiccation Tolerance of German Cockroaches (Dictyoptera: Blattellidae) Exposed to Moving Air

Rates of water loss and desiccation tolerance of German cockroaches, Blattella germanica (L.), exposed to moving air were determined in continuous exposure experiments using modified Ebeling choice boxes. Rates of water loss (g/g · d), based on changing wet mass, of each cockroach over time were modeled using an exponential equation, the coefficients of which were further analyzed to determine the effects of air velocity and body water composition. Water loss rates of all B. germanica stages examined increased with increasing air velocity. Median mortality times for cockroaches decreased exponentially with increasing air velocity. Adult males had the shortest median mortality times (63 and 26 hr at 0 and 4.75 m/sec) while large nymphs had the longest (293 and 120 hr at 0 and 4.75 m/sec). Percentages of total body water lost at the median mortality times decreases with increasing air velocity, therefore cockroaches can withstand greater %TBW. loss when desiccated more slowly.

Selection of Myeloid Progenitors Lacking BCR/ABL mRNA in Chronic Myelogenous Leukemia Patients After In Vitro Treatment With the Tyrosine Kinase Inhibitor Genistein

Chronic myelogenous leukemia (CML) is a clonal disorder of the hematopoietic stem cell characterized by a chimeric BCR/ABL gene giving rise to a 210-kD fusion protein with dysregulated tyrosine kinase activity. We investigated the effect of genistein, a protein tyrosine kinase inhibitor, on the in vitro growth of CML and normal marrow-derived multi-potent (colony-forming unit-mix [CFU-Mix]), erythroid (burst-forming unit-erythroid [BFU-E]), and granulocyte-macrophage (colony-forming unit-granulocyte-macrophage [CFU-GM]) hematopoietic progenitors. Continuous exposure of CML and normal marrow to genistein induced a statistically significant and dose-dependent suppression of colony formation. Genistein doses causing 50% inhibition of CML and normal progenitors were not significantly different for CFU-Mix (27 mumol/L v 23 mumol/L), BFU-E (31 mumol/L v 29 mumol/L), and CFU-GM (40 mumol/L v 32 mumol/L v 32 mumol/L). Preincubation of CML and normal marrow with genistein (200 mumol/ L for 1 to 18 hours) induced a time-dependent suppression of progenitor cell growth, while sparing a substantial proportion of long-term culture-initiating cells (LTC-IC) from CML (range, 91% +/- 9% to 32% +/- 3%) and normal marrow (range, 85% +/- 8% to 38% +/- 9%). Analysis of individual CML colonies for the presence of the hybrid BCR/ABL mRNA by reverse transcription-polymerase chain reaction (RT-PCR) showed that genistein treatment significantly reduced the mean +/- SD percentage of marrow BCR/ABL+ progenitors both by continuous exposure (76% +/- 18% v 24% +/- 12%, P < or = .004) or preincubation (75% +/- 16% v 21% +/- 10%, P < or = .002) experiments. Preincubation with genistein reduced the percentage of leukemic LTC-IC from 87% +/- 12% to 37% +/- 12% (P < or = .003). Analysis of individual colonies by cytogenetics and RT-PCR confirmed that genistein-induced increase in the percentage of nonleukemic progenitors was not due to suppression of BCR/ABL transcription. Analysis of nuclear DNA fragmentation by DNA gel electrophoresis and terminal deoxynucleotidyl transferase assay showed that preincubation of CML mononuclear and CD34+ cells with genistein induced significant evidence of apoptosis. These observations show that genistein is capable of (1) exerting a strong antiproliferative effect on CFU-Mix, BFU-E, and CFU-GM while sparing the more primitive LTC-IC and (2) selecting benign hematopoietic progenitors from CML marrow, probably through an apoptotic mechanism.

Validation of a short‐term toxicity test endpoint by comparison with longer‐term effects on larval red abalone Haliotis rufescens

AbstractExperiments were conducted to compare a short‐term 48‐h aquatic toxicity test endpoint of abnormal larval shell development with other, more clearly adverse effects. In similar experiments conducted with two different toxicants, zinc sulfate and bleached‐kraft mill effluent, red abalone (Haliotis rufescens) embryos were simultaneously exposed to identical dilution series and incubated for three different exposure periods: 48 h, 48 h followed by an 8‐d recovery period in clean seawater, and 10 d of continuous exposure. Abnormal larval shell development was assessed in the 48‐h short‐term tests, and inhibition of metamorphosis was assessed in the exposure‐recovery and continuous exposure experiments. For the zinc experiments, the median effective concentration (EC50) values for the 48‐h exposure, the exposure‐recovery experiment, and the continuous exposure experiment were 40, 34, and 32 μg/L zinc, respectively. For the bleached‐kraft mill effluent experiments, the EC50 values were 0.98, 0.76, and 0.69% effluent, respectively. Results indicate that toxicant concentrations causing abnormal larval shell development also inhibit metamorphosis and that larvae exposed to toxicant concentrations which inhibit larval shell development do not recover to metamorphose when transferred to clean seawater. None of the successfully metamorphosed postlarvae had deformed larval shells, indicating that shell deformity precludes survival past the planktonic stage. A longer (15‐d) experiment allowed measurement of postlarval shell length in exposed postmetamorphic abalone. Insignificant differences in postlarval shell length indicated that the timing of larval metamorphosis was similar regardless of toxicant exposure and that the effects of the toxicant was to inhibit rather than to delay metamorphosis.

Cell proliferation and DNA adducts in hamster tracheal epithelium exposed to benzo[ a]pyrene in organ culture

The effect of benzo[ a]pyrene (B[ a]P) on cell proliferation in cultured hamster tracheal epithelium was studied in relation to the formation of B[ a]P- DNA adducts. To this end, tracheae were isolated from Syrian golden hamsters, cut into rings and cultured in Ham's F12 medium. Then, the tracheal rings were exposed to 2 or 20 μ mB[ a]P, either continuously for 7 days or for 2 days followed by a 5-day recovery period without B[ a]P. At intervals rings were sampled for determination of cell proliferation (by means of the labelling index). In addition, B[ a]P- DNA adduct levels were determined in the continuous exposure experiment by means of in situ detection by immunofluorescence microscopy. After 2 days of exposure to 2 or 20 μ m B[ a]P, there was a significant increase in B[ a]P- DNA adduct level. A further, linear increase in B[ a]P- DNA adduct level, however, was only observed after continuous exposure to 20 μ m B[ a]P, whereas the adduct level in the 2 μ m continuous exposure group remained virtually the same. In unexposed tracheal epithelium an initial peak of cell proliferation was observed. This initial proliferation was significantly lower in the exposed samples. Only continuous exposure to 20 μ m B[ a]P steadily decreased the labelling index from day 2 to 7. It is concluded that the increase in B[ a]P- DNA adduct level is correlated with the reduction of cell proliferation in hamster tracheal epithelium exposed to B[ a]P in Ham's F12 medium.

Bioconcentration of polychlorinated dibenzo- p-dioxins and polychlorinated dibenzofurans in guppies after aqueous exposure to a complex PCDD/PCDF mixture: relationship with molecular structure

Guppies ( Poecilia reticulata) were exposed to a complex mixture of polychlorinated dibenzo- p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in water for 21 days. It is the first study in which accumulation data of 15 toxic dioxins and furans were quantified simultaneously in a continuous exposure experiment. First-order uptake rate constants ( k 1) and first-order elimination rate constants ( k 2) were calculated for the toxic, laterally substituted congeners. Bioconcentration factors (BCFs) were calculated from both the ratios of concentrations in fish and water and from the ratios of the rate constants. Dioxins and furans were selectively accumulated in fish tissue. The non-laterally substituted congeners were either not observed in fish tissue or showed lower BCF values than their laterally 2,3,7,8-substituted isomers. The log BCF values of laterally substituted congeners ranged from 3.90 ± 0.06 to 5.27 ± 0.07. BCF values were smaller than predicted by existing linear relationships with log K ow. Several phenomena were discussed with respect to the observed bioconcentration behaviour, such as limited bioavailability, reduced lipid solubility, reduced membrane permeability and biotransformation. Furthermore, the similarity between structure-activity relationships considering bioaccumulation in fishes and the Ah-affinity in mammals was discussed.

Enhancement of progesterone receptor levels by interferons in AE-7 endometrial cancer cells.

Interferon (IFN) has been reported to increase hormone receptor expression in breast cancer cells and to sensitize them to antiproliferative hormones. Endometrial cancer cells with high progesterone receptor (PR) level respond better to progesterone therapy than cells with either low or absent PR level. The effect of four different interferons (alpha and beta, both natural [n] and recombinant [r]) on cell proliferation and steroid receptor levels was investigated in the PR positive AE-7 human endometrial cancer cell line over a period of 12 days. Cells were exposed to 10,100 and 1000 IU/ml of each IFN either for 3 days or continuously for 12 days. Hormone receptors were determined by the monoclonal enzyme immunoassay. Chemosensitivity was evaluated with the adenosine triphosphate-cell viability assay. AE-7 has a low level of estrogen receptors, which was not significantly affected by IFN exposure. The four IFN showed significantly enhanced PR levels over 12 days in both the 3-day and continuous-exposure experiments. No significant difference of PR enhancement was observed between 3 days and continuous exposure to IFN. This increase of receptors did not appear to be dose related. IFN enhanced PR level to a maximum level of about two times control cells. IFN did not produce significant cytotoxicity. Antiproliferative activity was observed with nIFN beta and rIFN beta at 1000 IU/ml dose in continuous-exposure experiments, which showed survival values of 79% and 69% respectively, compared with control at day 12. These preliminary data on PR expression modulation support other studies, which have shown that IFN modulate hormone receptor expression and, therefore, may play a role in the treatment of endometrial cancer.

Physicochemical properties and antitumor activities of polymeric prodrugs of mitomycin C with different regeneration rates

Three types of conjugates of mitomycin C (MMC) with dextran ( M w: 70,000) (MMCD) were synthesized employing γ-aminobutyric acid (MMC(C4)D), ε-aminocaproic acid (MMC(C6)D), and ω-aminocaprylic acid (MMC(C8)D) and their physicochemical properties and antitumor activities were studied. MMC was released from MMCDs by chemical hydrolysis with different rates depending on the length of the spacer; i.e., half-lives (pH 7.4, 37°C) were 11.0, 24.2, and 42.2 h for MMC(C4)D, MMC(C6)D, and MMC(C8)D, respectively. MMCDs have a polycationic nature and were adsorbed on tumor cell surfaces. In a continuous exposure experiment, MMCD showed growth inhibitory activities against cultured L1210 mouse leukemia cells in proportion to the release rates of MMC. Activity of MMC(C4)D was the highest and comparable to free MMC. In a 1 h exposure experiment, the cytotoxicities of MMC(C6)D and MMC(C8)D, which showed strong interaction with tumor cells, were superior to free MMC while MMC(C4)D had only slight growth inhibitory effect. MMCDs prolonged the survival of mice bearing P388 leukemia in an i.p.-i.p. system. Especially, MMC(C6)D showed a superior effect and an excellent therapeutic index as compared with free MMC and other conjugates. Thus, the spacer length of MMCD was proved to be the determinant of the regeneration rate of MMC and subsequent antitumor activity.

The colony inhibition of a new chemotherapeutic agent (KW2152) against human lung cancer cell lines.

The human tumor colony assay was used to evaluate the effect of a new chemotherapeutic agent (KW2152) on colony inhibition of four non-small cell lung cancer cell lines and a mouse cell line. With continuous exposure experiments, KW2152 induced greater than or equal to 70% colony inhibition of PC-7 (human adenocarcinoma), PC-10 (human squamous cell) and PC-13 (human large cell) at a drug concentration of 10 mcg/ml. In one hour exposure experiments, KW2152 caused a significant reduction in colony formation (less than or equal to 30% of control) only at the highest concentration tested (100 mcg/ml). KW2152 showed significant in vitro activity against human non-small cell lung cancer cell lines. Due to these promising results, it was suggested that KW2152 should be evaluated in clinical trials.