Toxicokinetics of acrylamide and glycidamide in B6C3F mice

Acrylamide (AA) is a widely studied industrial chemical that is neurotoxic, mutagenic to somatic and germ cells, and carcinogenic in rodents. The recent discovery of AA at ppm levels in a wide variety of commonly consumed foods has energized research efforts worldwide to define toxic mechanisms, particularly toxicokinetics and bioavailability. This study compares the toxicokinetics of AA and its epoxide metabolite glycidamide (GA) in serum and tissues of male and female B6C3F1 mice following acute dosing by intravenous, gavage, and dietary routes at 0.1 mg/kg AA or intravenous and gavage dosing with an equimolar amount of GA. AA was rapidly absorbed from oral dosing, was widely distributed to tissues, was efficiently converted to GA, and increased levels of GA-DNA adducts were observed in liver after complete elimination from serum. GA dosing also resulted in rapid absorption, wide distribution to tissues, and produced liver DNA adduct levels that were approximately 40% higher than those from an equimolar dose of AA. While oral administration was found to attenuate AA bioavailability to 23% from the diet and to 32-52% from aqueous gavage, a first-pass effect or other kinetic change resulted in higher relative internal exposure to GA when compared to the intravenous route. A similar effect on relative GA exposure was also evident as the administered dose was reduced, which suggests that as dosing rate decreases, the conversion of AA to GA is more efficient. These findings are critical to the assessment of genotoxicity of AA at low doses in the food supply, which appears to depend on total exposure to GA.

Discriminant Function Analyses of Liver-Specific Carcinogens

The ability to predict organ-specific carcinogenicity would aid FDA reviewers in evaluating new chemical applications. A NCTR liver cancer database (NCTRlcdb) containing 999 compounds has been developed with three sets of descriptors. The NCTRlcdb has Cerius2, Molconn-Z, and (13)C NMR descriptors for each compound. Each compound in the database was assigned a liver cancer or a nonliver cancer classification. Compounds within the NCTRlcdb were evaluated for liver-specific carcinogenicity using partial least squares principal component discriminant function (PLS-DF) modeling. PLS-DF models based on estimated a priori classification probabilities of 0.29 for liver cancer and 0.71 for noncancer yielded an overall predictability of 70.6% which was comprised of a liver cancer sensitivity of 18.8% and a noncancer specificity of 90.8%. PLS-DF models based on equal a priori classification probabilities, 0.50 for liver cancer and 0.5 for noncancer, yielded an overall predictability of 61.0% which was comprised of a liver cancer sensitivity of 50.5% and a noncancer specificity of 65.3%.

Water-Holding Capacity in Chicken Breast Muscle is Enhanced by Pyruvate and Reduced by Creatine Supplements

In commercial production, chickens are subjected to feed withdrawal prior to slaughter and exposed to stress during transport and handling of the animals at the slaughterhouse; this causes plasma glucose and glycogen stores in liver and muscle to decrease, which has a negative impact on meat quality. The aim of the present study was to investigate how supplementation of the energy complements creatine and pyruvate during the fasting period would affect postmortem pH decrease, water-holding capacity, and color of the meat. Female Ross 208 broilers were supplemented with glucose combined with either pyruvate or creatine via the drinking water for 18 or 42 h prior to slaughter, i.e., before and throughout the fasting period. Chickens were slaughtered at 42 or 43 d of age. Temperature and pH were measured at 1, 10, 30, and 45 min and 1, 2, 4, 8, and 12 h postmortem. The results showed that the pyruvate and glucose supplementation increased the pH at 45 min postmortem by 0.25 units and decreased drip loss of musculus pectoralis major (PM) by 50 to 65% in chickens supplemented for 42 h. The creatine and glucose supplementation reduced pH at 3 and 4 h postmortem by 0.32 to 0.42 units, increased the lightness (L*) by 2.3 to 5.6 units, and increased drip loss by 51 to 137% in the PM of chickens supplemented for 18 and 42 h. Pyruvate and glucose supplementation thus appear beneficial but whether this is concomitant with an overall improvement in meat quality remains to be determined.

The prediction of methylmercury elimination half-life in humans using animal data: a neural network/rough sets analysis

Artificial neural networks and Rough Sets methodology have been utilized to predict human pharmacokinetic elimination half-life data based on animal data training sets. Methylmercury (Hg) pharmacokinetic data was obtained from 37 literature references, which provided data on species, gender, age, weight, route of administration, dose, dose frequency, and elimination half-life based on either whole-body Hg analysis or blood Hg analysis. Data were categorized into various formats for analysis comparisons. Rough Sets methodology was utilized to identify and remove redundant independent variables. Artificial neural networks were used to produce models based on the animal data, which were in turn used to predict and compare to the human elimination half-life values. These neural network predictions were compared to allometric graphical plots of the same data. The best artificial neural network prediction was based on a "thermometer" categorical representation of the data.

Ascorbic acid, alpha-tocopherol, and oregano supplements reduce stress-induced deterioration of chicken meat quality

In order to ameliorate a negative effect of stress on meat quality characteristics, chickens were fed a diet supplemented with a combination of ascorbic acid (1,000 ppm) and alpha-tocopherol (200 ppm) or oregano (3%), which has a high content of antioxidants. Chickens were slaughtered by cervical dislocation in the stable (no stress) or after transport and electrical stunning at the slaughter plant (stress). Activities of antioxidative enzymes (catalase, superoxide dismutase, and glutathion peroxidase) in pectoralis major (PM), iliotibialis (IL), and liver were unaffected by supplementation. However, erythrocyte stability, which is a more complex model system for determining oxidative status, increased with ascorbic acid-alpha-tocopherol supplementation and tended to increase after oregano supplementation. In nonstressed birds, this improved antioxidative status was reflected in decreased TBA-reactive substances (TBARS) in PM and liver of ascorbic acid-alpha-tocopherol-supplemented chickens and likewise in liver from oregano-supplemented chickens compared to that of nonstressed control birds. However, postmortem temperature, pH, and water-holding capacity were not affected by supplementation. Drip loss from oregano-supplemented chickens showed increased protein oxidation in specific bands, but this did not relate to water-holding capacity or antioxidative status. When exposed to stress, the concentration of TBARS in the control animals increased in PM and IL. Ascorbic acid-alpha-tocopherol supplementation protected IL, and oregano supplementation protected PM from stress-induced increases in TBARS. This differential effect between muscles may indicate differences in protection mechanisms. In conclusion, ascorbic acid-alpha-tocopherol and oregano supplements to chickens protect against stress-induced increase in TBARS, in different muscles.

Plasma levels of parent compound and metabolites after doses of either d-fenfluramine or d-3,4-methylenedioxymethamphetamine (MDMA) that produce long-term serotonergic alterations

Plasma levels of parent compounds and metabolites were determined in adult rhesus monkeys after doses of either 5mg/kg d-fenfluramine (FEN) or 10mg/kg d-3, 4-methylenedioxymethamphetamine (MDMA) i.m. twice daily for four consecutive days. These treatment regimens have been previously shown to produce long-term serotonin (5-HT) depletions. Peak plasma levels of 2.0+/-0.4 microM FEN were reached within 40min after the first dose of FEN, and then declined rapidly, while peak plasma levels (0.4+/-0.1 microM) of the metabolite norfenfluramine (NFEN) were not reached until 6h after dosing. After the seventh (next to last) dose of FEN, peak plasma levels of FEN were 35% greater than after the first dose while peak NFEN-levels were 500% greater. The t(1/2) for FEN was 2.6+/-0.3h after the first dose and 3.2+/-0.2h after the seventh. The estimated t(1/2) for NFEN was more than 37.6+/-20.5h. Peak plasma levels of 9.5+/-2.5 microM MDMA were reached within 20min after the first dose of MDMA, and then declined rapidly, while peak plasma levels (0.9+/-0.2 microM) of the metabolite 3,4-methylenedioxyamphetamine (MDA) were not reached until 3-6h after dosing. After the seventh (next to last) dose of MDMA, peak plasma levels of MDMA were 30% greater than the first dose while peak MDA levels were elevated over 200%. The t(1/2) for MDMA was 2.8+/-0.4h after the first and 3.9+/-1.1h after the seventh dose. The estimated t(1/2) for MDA was about 8.3+/-1.0h. Variability in plasma levels of MDMA and MDA between subjects was much greater than that for FEN and NFEN. This variability in MDMA and MDA exposure levels may have lead to variability in the subsequent disruption of some behaviors seen in these same subjects. There were 80% reductions in the plasma membrane-associated 5-HT transporters 6 months after either the FEN or MDMA dosing regimen indicating that both treatments produced long-term serotonergic effects.

Feed and strain effects on the use of outdoor areas by broilers

1. The use of outdoor areas by two broiler strains, known to have different growth rates and with access to either moderate (M) or low (L) energy feeds, was examined to assess the consequences for production, meat quality, health and welfare. 2. Sixteen groups of either Ross 208 (ROSS) or a Labresse cross (LAB) were fed either feed M or L. They were raised indoors until 42 d of age when groups of 102 birds were moved to outdoor houses with free access to an outdoor area. 3. The number of chickens standing and lying, respectively, in each of 5 zones in the outdoor area were recorded at intervals throughout the outdoor growth period until slaughter at 84 d of age. Production variables were measured, and gait, feather condition, litter quality, and dermal lesions on foot-pads and hocks were scored together with objective meat quality measures. 4. Both strains showed a diurnal rhythm with most birds observed outside around sunrise and before sunset. Feed and strain both affected the distribution of the birds on the outdoor area, with more birds on feed M than L observed outside, and with more LAB birds outside and using more of the outdoor area than ROSS. This was reflected in some of the carcase and meat quality measures. Feather pecking and cannibalism only occurred in LAB. 5. ROSS was found to have a faster growth rate, poorer litter quality, more dermal lesions and impaired mobility, reflected in low usage of outdoor area and poor gait score compared with LAB. 6. This together with the presence of pectoral myopathies make ROSS unsuitable for 12 week growth in free range production systems. The occurrence of feather pecking and cannibalism in LAB make this particular Labresse cross questionable for meat-type poultry production.

Toxicokinetics of riddelliine, a carcinogenic pyrrolizidine alkaloid, and metabolites in rats and mice

Riddelliine is a representative pyrrolizidine alkaloid, a class of naturally occurring toxic phytochemicals present in plant species worldwide. Human exposure to pyrrolizidine alkaloids occurs through consumption of herbal dietary supplements, including comfrey, and through contaminated livestock products (e.g., milk). A recently completed 2-year bioassay of riddelliine carcinogenicity showed that male and female rats and male mice, but not female mice, developed liver tumors. The toxicokinetics of riddelliine and two metabolites, the N-oxide and retronecine, were determined in serum following an oral gavage dose in male and female rats and mice using a validated liquid chromatography-electrospray mass spectrometric method. The results are consistent with extensive metabolism of riddelliine and its more polar metabolites prior to excretion. It is concluded that factors other than toxicokinetics are responsible for the observed species/sex specificity of gross toxicity or liver tumor induction in rats and mice.

Green tea extract only affects markers of oxidative status postprandially: lasting antioxidant effect of flavonoid-free diet

Epidemiological studies suggest that foods rich in flavonoids might reduce the risk of cardiovascular disease and cancer. The objective of the present study was to investigate the effect of green tea extract (GTE) used as a food antioxidant on markers of oxidative status after dietary depletion of flavonoids and catechins. The study was designed as a 2 x 3 weeks blinded human cross-over intervention study (eight smokers, eight non-smokers) with GTE corresponding to a daily intake of 18.6 mg catechins/d. The GTE was incorporated into meat patties and consumed with a strictly controlled diet otherwise low in flavonoids. GTE intervention increased plasma antioxidant capacity from 1.35 to 1.56 (P<0.02) in postprandially collected plasma, most prominently in smokers. The intervention did not significantly affect markers in fasting blood samples, including plasma or haemoglobin protein oxidation, plasma oxidation lagtime, or activities of the erythrocyte superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase. Neither were fasting plasma triacylglycerol, cholesterol, alpha-tocopherol, retinol, beta-carotene, or ascorbic acid affected by intervention. Urinary 8-oxo-deoxyguanosine excretion was also unaffected. Catechins from the extract were excreted into urine with a half-life of less than 2 h in accordance with the short-term effects on plasma antioxidant capacity. Since no long-term effects of GTE were observed, the study essentially served as a fruit and vegetables depletion study. The overall effect of the 10-week period without dietary fruits and vegetables was a decrease in oxidative damage to DNA, blood proteins, and plasma lipids, concomitantly with marked changes in antioxidative defence.

Decreased in vitro interaction between p53 and nuclear stress proteins in the p53-deficient mouse

In a previous study, the strength of the interaction between the nuclear stress proteins (sps) 25a, 70i, 72c, and 90 and the tumor suppressor protein p53 was determined by an in vitro fluorescence binding assay. The relative binding of the individual sps with p53, derived from the bone marrow of transgenic mice heterozygous at the p53 locus (p53+/-), was reduced compared to the interaction of sps and p53 derived from wild-type (p53+/+) mice. In order to determine if the genotype of the p53 donor or the genotype of the sp donor determined the binding efficiency, p53 expression was induced by retinoic acid and sp synthesis by bleomycin. P53 derived from either wild-type or heterozygous animals was cross-reacted with nuclear sps obtained from either wild-type or heterozygous animals. Each of the sps, 25a, 70i, 72c, and 90, bound to wild-type p53 with a similar efficiency, irrespective of the genotype of the sp donor mouse (p53+/+ or p53+/-). In contrast, when the sp interaction with p53 obtained from the heterozygous mouse was measured, the relative value of the fluorescence complex was significantly reduced. The data suggest that the strength of the interaction between p53 and nuclear sps is related to the genotype of the p53 donor, and not to the genotype of the animals from which the sps are derived.

Analysis of methylmercury disposition in humans utilizing a PBPK model and animal pharmacokinetic data

Physiologically based pharmacokinetic (PBPK) models are excellent tools to aid in the extrapolation of animal data to humans. When the fate of the chemical is the same among species being compared, animal data can appropriately be considered as a model for human exposure. For methylmercury exposure, sufficient data exist to allow comparison of numerous mammalian species to humans. PBPK model validation entails obtaining blood and tissue concentrations of the parent chemical and metabolite(s) at various times following a known exposure. From ethical and practical considerations, human tissue concentrations following a known exposure to an environmental toxicant are scarce. While animal-to-human extrapolation demands that sufficient human data exist to validate the model, the validation requirements are less stringent if multiple animal models are utilized within a single model template. A versatile PBPK model was used to analyze the distribution and elimination of methylmercury and its metabolite, inorganic mercury. Uniquely, the model is formed in a generic way from a single basic template during the initial program compilation. Basic parameters are defined for diffferent PBPK models for mammalian species that span a relatively large range of sizes. In this article, the analyses include 12 species (mouse, hamster, rat, guinea pig, cat, rabbit, monkey, sheep, pig, goat, cow, and human). Allometric (weight-based) correlations of tissue binding coefficients, metabolism rate constants, and elimination parameters for both methylmercury and inorganic mercury are presented for species for which sufficient data are available. The resulting human model, in accord with the animal models, predicts relatively high inorganic mercury levels in the kidneys long after the disappearance of methylmercury from the blood.

Resonant scattering and mode coupling in two-dimensional textured planar waveguides

A heuristic formalism is developed for efficiently determining the specular reflectivity spectrum of two-dimensionally textured planar waveguides. The formalism is based on a Green's function approach wherein the electric fields are assumed to vary little over the thickness of the textured part of the waveguide. Its accuracy, when the thickness of the textured region is much smaller than the wavelength of relevant radiation, is verified by comparison with a much less efficient, exact finite difference solution of Maxwell's equations. In addition to its numerical efficiency, the formalism provides an intuitive explanation of Fano-like features evident in the specular reflectivity spectrum when the incident radiation is phase matched to excite leaky electromagnetic modes attached to the waveguide. By associating various Fourier components of the scattered field with bare slab modes, the dispersion, unique polarization properties, and lifetimes of these Fano-like features are explained in terms of photonic eigenmodes that reveal the renormalization of the slab modes due to interaction with the two-dimensional grating. An application of the formalism, in the analysis of polarization-insensitive notch filters, is also discussed.

A mechanistic approach to modelling the risk of liver tumours in mice exposed to fumonisin B1 in the diet

Data from the National Toxicology Program's carcinogenesis study of fumonisin B1 in B6C3F1 mice, conducted at the National Center for Toxicological Research, were used to fit the Moolgavkar-Venzon-Knudson (MVK) two-stage, clonal-expansion model of carcinogenesis. In addition to tumour data from the conventional 2-year bioassay, the study included data on tissue weights, cell proliferation, cell death, and sphingolipid metabolism in primary target organs. The model was used to predict 2-year liver tumour rates in female and male mice based on differences among dose groups in the effect of fumonisin B1 on the growth of normal tissue and on the proliferation of preneoplastic cells as a compensatory response to sphinganine-induced cell death. Fumonisin B1 was assumed to be non-genotoxic, i.e. the model did not include any effect of fumonisin B1 on either of the two mutation rates of the MVK model. The model was able to reproduce reasonably well the observed tumour rates in both female and male mice, predicting substantially increased rates above background only at the highest doses of fumonisin B1 in females.

Tissue sphinganine as a biomarker of fumonisin-induced apoptosis

NCTR measured sphinganine concentrations in the livers of mice and in the livers and kidneys of rats in conjunction with a tumour bioassay. In our model of the tumour incidence, target-tissue levels of sphinganine serve as a biomarker for a dose response of fumonisin B1 on cell death. Initially we questioned the utility of sphinganine levels in this role because they were highly variable when compared across time points. In spite of this concern, a conceptual framework and data are presented that support the use of sphinganine as a biomarker for a dose response of fumonisin B1 on cell death. This framework is reasonably consistent with observed sphinganine concentrations in the examined tissues, the literature on fumonisin's effects on sphingolipid synthesis, and our hypothesized mechanism through which fumonisin B1 increases age-specific tumour incidence.

Correlation of blood cholinesterase levels with toxicity of sarin in rats

The dose-mortality response curve for sarin when administered to pregnant rats is extremely steep. The pregnant animal either died during the treatment or survived with no observable fetal toxicity. Animals that died displayed many symptoms characteristic of anticholinesterase toxicity. The present study was conducted to determine whether the maternal deaths, clinical observations, and/or weight loss could be correlated with baseline blood cholinesterase levels in individual animals. Cholinesterase levels (plasma and erythrocyte) were obtained prior to, during, and following treatment of nonpregnant rats by gavage with 380 microg/kg/d sarin for 10 d. After the first dose, there was a drop in the plasma cholinesterase levels, which then remained low throughout the dosing period. There was a statistically significant correlation between body weight loss and plasma cholinesterase levels of the sarin dosed animals. The surviving animals also had lower plasma cholinesterase levels and lower body weights, both of which recovered on the cessation of dosing. The erythrocyte cholinesterase levels were not different between treated and nontreated rats. Neither plasma or erythrocyte baseline cholinesterase levels nor relative or absolute cholinesterase decline values could be used as predictors of mortality from sarin administration in rats.

Dose-response of retinoic acid induced stress protein synthesis and teratogenesis in mice

Stress proteins are synthesized in response to a variety of stressors, including several teratogenic agents. However, their role, if any, in the teratogenic process is unknown. We have previously demonstrated that all-trans-retinoic acid administered to pregnant CD-1 mice on gestational day 11 or 13 produced limb defects and cleft palate near term in a dose-responsive manner. This chemical also induced the synthesis of several nuclear stress proteins in embryonic tissues within several hours of dosing. The stress proteins were only observed in tissues that eventually became malformed and not in tissues that appeared normal at term. In the current work, we examined the stress response in embryonic target tissues after several different doses of retinoic acid. The nuclear stress proteins were synthesized in a dose-related manner and at a lower retinoic acid dose than doses producing malformations in the corresponding tissue at birth. Each individual stress protein and the total stress protein response were highly correlated, across dose, with the respective malformations observed at term.

Cement solidification of simulated off-gas condensates from vitrification of low-level nuclear waste solutions

Solidification in a cementitious matrix is a viable alternative for low-level nuclear waste management; it is therefore important to understand the behavior and properties of such wasteforms. We have examined the cementitious solidification of simulated off-gas waste streams resulting from the vitrification of low-level nuclear waste. Different possible methods for scrubbing the off-gasses from a vitrifier give rise to three possible types of waste compositions: acidic (from aqueous dissolution of volatile NOx and POx carried over from the vitrifier), basic (from neutralizing the former with sodium hydroxide), and fully carbonated (arising from a direct-combustion vitrifier). Six binder compositions were tested in which ordinary Portland cement was replaced at different proportions by fly ash and/or ground granulated blast furnace slag. A high solution to binder ratio of 1l/1 kg was used to minimize the volume of the wasteform and 10% attapulgite clay was added to all mixes to ensure that the fresh mix did not segregate prior to setting. The 28-day compressive strengths decreased when a high proportion of cement was replaced with fly ash, but were increased significantly when the cement was replaced with slag. The heats of hydration at early age for the various solids compositions decreased when cement was replaced with either fly ash or slag; however, for the fly ash mix the low heat was also associated with a significant decrease in compressive strength. High curing temperature (60 degrees C) or the use of extra-fine slag did not significantly affect the compressive strength. Recommendations for choice of binder formulations and treatment of off-gas condensates are discussed.

Ecology of Borrelia burgdorferi in ticks (Acari: Ixodidae), rodents, and birds in the Sierra Nevada foothills, Placer County, California

This study examined the prevalence of Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner in host-seeking adult and nymphal Ixodes pacificus Cooley & Kohls and estimated the I. pacificus infestation and B. burgdorferi infection of rodent and avian hosts in the western Sierra Nevada foothills of northern California. Additionally, we identified species likely to participate in an enzootic cycle for B. burgdorferi in this yellow pine transition habitat. Evidence of infection with B. burgdorferi was identified in 7.3 and 5.4% of host-seeking I. pacificus adults and nymphs, respectively. Mean numbers of I. pacificus observed on rodents were 1.15 for Neotoma fuscipes Baird and 0.18 for Peromyscus spp. One of 104 ear punch tissues obtained from woodrats and none from 49 Peromyscus spp. yielded B. burgdorferi. A total of 291 collected birds representing 34 species had a mean of 0.27 I. pacificus per bird. The mean I. pacificus infestation of ground-dwelling birds was 2.5 ticks per bird. Forty-nine of 92 (53%) blood smears collected from birds were reactive to a B. burgdorferi specific antibody. This study presents the identification of a B. burgdorferi-like spirochete in birds in western North America. The tick burden and spirochete infection of birds suggests that birds may be involved in a local B. burgdorferi enzootic cycle and likely participate in the transport of ticks and spirochetes to other locations while rodents from this site do not appear to be major contributors.

The effect of grape-skin extract on oxidative status

Epidemiological studies indicate that moderate alcohol consumption, particularly wine, reduce the risk of CHD. The present study was designed to investigate the effect of grape-skin extract on markers of oxidative status. The study was designed as a randomised crossover. A diet with a low content of flavonoids was served with strict control of intake in two consecutive 1-week intervention periods to fifteen subjects (nine women, six men) divided randomly into two groups. During one of the weeks the subjects from either group consumed 200 ml grape-skin extract in water (1 mg extract/ml) at each of three daily meals (31.3 mg total phenolics, including 9.0 mg catechin). An increased activity of glutathione reductase and a borderline increase of glutathione peroxidase activity in erythrocytes were observed after grape-skin intervention, while the intervention had no significant effect on superoxide dismutase or catalase. Likewise, no effect was found on 2-aminoadipic semialdehyde (AAS) residues, a plasma protein oxidation product, or on malondialdehyde in plasma or in LDL, which are markers of lipoprotein oxidation. A marginal effect of grape-skin intervention was observed on plasma ascorbate levels. Intake of the experimental diet significantly reduced plasma vitamin C and plasma AAS in both groups. This effect was most pronounced in the particular week with no grape-skin extract addition. We speculate that grape-skin extract may have a sparing effect on vitamin C. The effects of the experimental diet may be partly ascribed to a low content of several fruit- and vegetable-related antioxidants like flavonoids and vitamin C and a relatively high content of carrot-derived antioxidants, such as carotenes.

Mathematical modeling of human embryonic and fetal growth rates

A mathematical model for human embryonic/fetal growth data from implantation to birth is developed. In previous work, it was shown that an unbiased estimate for human fetal growth data from about day 50 post-conception until term could be calculated from the Gompertz equation. This period represents a range of embryonic/fetal weights from one to 3500 g. When the Gompertz equation is extended, with no change of parameters, to the prenatal period before 50 days, the predicted weights have a consistent bias which might have a biological basis. Early embryonic growth immediately following fertilization is exponential; i.e., one cell goes to 2, then 4, then 8... etc., with essentially no decrease in relative growth rate. Except for possible small changes in cell size and cell mitosis cycle time, such exponential growth can be considered as a special case of the Gompertz equation with a, the relative rate of decrease of the relative growth rate, equal to zero. The relative growth rate begins to decrease about 20 days post-conception, at the time of cell differentiation into organ precursors. Although the "Hayflick Limit" of the maximum of 50 to 60 cell divisions for human cells would tend to cause a decrease in growth rate, it can be shown that the effect is insignificant during embryonic/fetal growth. The observed decrease in the growth rate might be a result of a decreasing fraction of cells in the pool of dividing cells. For the Gompertz equation model, a at this time changes from zero to a positive number. Analysis of fetal growth data shows that a rapidly becomes large and then decreases over a period of several days to become a constant positive value for the remainder of the prenatal term. Good fits of empirical embryonic/fetal growth data were obtained by nonlinear regression with calculation of the embryonic/fetal weights through numerical integration of the differential Gompertz equations and the functionality of alpha.

[Polyphenolic antioxidants in fruit juice. Urinary excretion and effects on biological markers for antioxidative status]

This intervention study was designed as cross-over (four women, one man) with three doses of black currant/apple (1:1) juice (750, 1000, and 1500 mL) for one week corresponding to an intake of 4.8, 6.4, and 9.6 mg quercetin per day. Urinary excretion of quercetin increased significantly with dose and with time. The fraction excreted in urine was constant 0.29-0.47%. Plasma quercetin did not change with juice intervention. Plasma ascorbate increased during intervention due to ascorbate from the juice. Total plasma malondialdehyde decreased with time during 1500 mL juice intervention. Plasma protein 2-adipic semialdehyde residues, increased with time and dose, and glutathione peroxidase increased with juice dose, whereas other selected markers of oxidative status did not change. These effects might be related to several components of the juice and cannot be attributed solely to its quercetin content.

Retinal pigment epithelial cell function on substrates with chemically micropatterned surfaces

Model substrates with desired chemical micropatterns were fabricated using a microcontact printing technique. The substrate surfaces contained organized arrays of circular glass domains with a diameter of either 10 or 50 microm surrounded and separated by regions modified with octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs). The effects of surface patterning on in vitro cell attachment, proliferation, morphology, and cytoskeletal organization were evaluated using a human retinal pigment epithelium (RPE) cell line. Both micropatterns affected initial RPE cell attachment, limited cell spreading, and promoted the characteristic cuboidal cell morphology throughout the culture period. In contrast, RPE cells on plain glass control were elongated and appeared fibroblast-like prior to confluence. In addition, cells seeded at 30,000 cell/cm2 on the patterned surfaces maintained a normal pattern of actin and cytokeratin expression, and formed confluent monolayers within 4 days of culture. The cell density increased about 30-fold on both micropatterns by day 7. These results show that it is feasible to control RPE cell shape and expression of differentiated phenotype using micropatterned surfaces.

Induction of stress proteins by electromagnetic fields in cultured HL-60 cells

HL-60 cells in culture were exposed for 2 h to a sinusoidal 0.1 or 1 mT (1 or 10 Gauss) magnetic field at 60 Hz and pulse labeled after exposure with radioactive isotopes by incubation by using either [(35)S]methionine, [(3)H]leucine, or [(33)P]phosphate. The radioactive labels were incorporated into cellular proteins through synthesis or phosphorylation. Proteins were extracted from electrostatically sorted nuclei, and the heat shock/stress proteins (sp) were analyzed for synthesis and phosphorylation by two-dimensional polyacrylamide gel electrophoresis. In the control cultures (no exposure to the magnetic field), sp 72c (cognate form) was faintly observed. A 0.1 mT exposure did not show sp metabolism to be different from that of the controls; however, after a 1 mT exposure of the HL-60 cells, sp 70i (inducible form) was synthesized ([(35)S]methionine incorporation). Sp 90 was not synthesized at either field level, but was phosphorylated ([(33)P]phosphate incorporation) in the 1 mT exposure. Sp 27 (isoforms a and b) was induced after a 1 mT exposure as reflected by labeling with [(3)H]leucine. These sps were not detected after a 0.1 mT exposure. After a 1 mT exposure and labeling with [(33)P], sp 27 isoforms b and c were phosphorylated whereas isoform 'a' was not observed. Sps 70i, 72c, and 90 were identified by commercial sp antibodies. Likewise, polypeptides a, b, and c were verified as sp 27 isoforms by Western blotting. Statistical evaluation of sp areas and densities, determined from fluorographs by Western-blot analysis, revealed a significant increase in sps 90 and 27a after a 1 mT magnetic field exposure. The 1 mT magnetic field interacts at the cellular level to induce a variety of sp species. Bioelectromagnetics 20:347-357, 1999. Published 1999 Wiley-Liss, Inc.

A direct comparison of the activities of two humanized respiratory syncytial virus monoclonal antibodies: MEDI-493 and RSHZl9

Two humanized monoclonal antibodies, MEDI-493 and RSHZ19, were developed independently as potential improvements over RSV-IGIV for prevention of respiratory syncytial virus (RSV) infection. RSV-IGIV is a polyclonal human antibody preparation for intravenous infusion enriched for RSV neutralizing activity. A phase III clinical trial showed that MEDI-493 significantly reduced hospitalizations due to RSV infection. In a separate trial, RSHZ19 failed to show significant efficacy. In new studies, the in vitro and in vivo activities of MEDI-493 and RSHZ19 were compared to determine whether the different clinical results are related to differences in biologic activity. MEDI-493 was consistently 4- to 5-fold more potent than RSHZ19 in antigen binding, RSV neutralization, and fusion inhibition assays. Although both MEDI-493 and RSHZ19 were effective against A and B subtypes of RSV in the cotton rat model of RSV infection, 2- to 4-fold higher doses of RSHZ19 were required for similar protection. The enhanced activity of MEDI-493 compared with RSHZ19 may, in part, explain its better clinical effect.