Cross study analyses of SEND data: toxicity profile classification.

A SEND toxicology data transformation, harmonization and analysis platform was created to improve the identification of unique findings related to the intended target, species, and duration of dosing using data from multiple studies. The lack of a standardized digital format for data analysis had impeded large-scale analysis of in vivo toxicology studies. The CDISC SEND standard enables the analysis of data from multiple studies performed by different laboratories. This work describes methods to analyze data and automate cross study analysis of toxicology studies. Cross study analysis can be used to understand a single compound's toxicity profile across all studies performed and/or to evaluate on-target versus off-target toxicity for multiple compounds intended for the same pharmacological target. This work involved development of data harmonization/transformation strategies to enable cross-study analysis of both numerical and categorical SEND data. Four de-identified SEND data sets from the BioCelerate database were used for the analyses. Toxicity profiles for key organ systems were developed for liver, kidney, male reproductive tract, endocrine system, and hematopoietic system using SEND domains. A Cross-Study Analysis dashboard with a built-in user-defined scoring system was created for custom analyses, including visualizations to evaluate data at the organ system level and drill down into individual animal data. This data analysis provides the tools for scientists to compare toxicity profiles across multiple studies using SEND. A cross-study analysis of two different compounds intended for the same pharmacological target is described and the analyses indicate potential on-target effects to liver, kidney, and hematopoietic systems.

Oblique wrinkles.

We prove theoretically that when a soft solid is subjected to an extreme deformation, wrinkles can form on its surface at an angle that is oblique to a principal direction of stretch. These oblique wrinkles occur for a strain that is smaller than the one required to obtain wrinkles normal to the direction of greatest compression. We go on to explain why they will probably never be observed in real-world experiments.This article is part of the themed issue 'Patterning through instabilities in complex media: theory and applications.'

Temporal gene expression analysis of monolayer cultured rat hepatocytes.

The use of cultured primary hepatocytes within toxicology has proven to be a valuable tool for researchers, however, questions remain with regard to functional differences observed in these hepatocytes relative to the intact liver. Cultured hepatocytes have typically been described as dedifferentiated, a classification based upon the investigation of a few key cellular processes or hepatocellular markers. In the present study, parallel expression monitoring of approximately 8700 rat genes was used to characterize mRNA changes over time in hepatocyte cultures using Affymetrix microarrays. We isolated and labeled mRNA from whole rat livers, hepatocyte-enriched cell pellets, and primary cultured hepatocytes (4, 12, 24, 48, and 72 h postplating), and hybridized these samples to microarrays. From these data, several pairwise and temporal gene expression comparisons were made. Gene expression changes were confirmed by RT/PCR and by performing replicate experiments and repeated hybridizations using a rat toxicology sub-array that contained a 900-gene subset of the 8700-gene rat genomic microarray. PCR data qualitatively reproduced the temporal patterns of gene expression observed with microarrays. Cluster analysis of time course data using self-organizing maps (SOM) revealed a classic hepatocyte dedifferentiation response. Functional grouping of genes with similar transcriptional patterns showed time-dependent regulation of phase I and phase II metabolizing enzymes. In general, cytochrome P450 mRNA expression was repressed, but expression of phase II metabolizing enzymes varied by class (upregulation of glucuronidation, downregulation of sulfation). Potential metabolic targets for toxic insult, such as glutathione metabolism, gluconeogenesis, and glycolysis, were also affected at the transcriptional level. Progressive induction of several genes associated with the cellular cytoskeleton and extracellular matrix was observed in accord with physical changes in cell shape and connectivity associated with cellular adhesion. Finally, many transcriptional changes of genes involved in critical checkpoints throughout the hepatocyte cell cycle and differentiation process were observed. In total, these data establish a more comprehensive understanding of hepatocellular dedifferentiation and reveal many novel aspects of physiological and morphological hepatocyte adaptation. An assembly of all transcripts that demonstrated differential expression in this study can be found in the Supporting Information.

A novel repeated sequence DNA originated from a Tc1-like transposon in water green frog Rana esculenta.

We have identified and characterized a highly repetitive family, called R.e./Tc1 in the genome of the green water frog Rana esculenta. This family consists of tandemly repeated sequences, localized at the centromeric regions of chromosomes as shown by Southern blot and 'in situ' hybridization. The repeat unit contains a residue of a Tc1-like transposon by Haematobia irritans fly, bordered by two short direct repeats of 9 bp. Tc1 remnant lays near a sequence identical to Homo sapiens Werner syndrome gene stretch. These sequence data suggest that R.e./Tc1 element was probably originated from a transposition event and a duplication via DNA mechanism of the R.e./Tc1 unit that could give rise to the observed tandem array.

Novel methylation at GpC dinucleotide in the fish Sparus aurata genome.

To date, vertebrate DNA has been found methylated at the 5' position of cytosine exclusively in dinucleotide CpG or CpNpG stretches. On the the other hand, we determined that cytosine was methylated unusually in dinucleotide GpC at 5'-GGCC-3' sequences in the teleost Sparus aurata EcoRI satellite DNA family. This finding is the first example of methylated GpC sequences in the eukaryotic genomes. At this regard, we have examined the relative methylation levels at this site of the highly repetitive EcoRI satellite DNA family from Sparus aurata different tissues. The EcoRI repeat was remarkably more methylated in male germ cells but hypomethylated in female germ cells at the Hae III restriction site (GpC). The novel modification and the differential methylation pattern suggest that EcoRI satellite could have a structural and/or functional role at the centromeres of Sparus aurata.

Identification of a new gene encoding pericentromeric dodeca-satellite binding protein in Drosophila melanogaster.

Dodeca-satellite (CCCGTACTCGGT)n is a type of tandemly repeated DNA sequence located in the pericentromeric region of the third chromosome of Drosophila melanogaster and that cross-hybridizes with DNA from other species such as Arabidopsis, mouse and human. This evolutionary conservation suggests that dodeca-satellite might play an important role in the centromeric function. Therefore, the aim of our research was the isolament of genes encoding proteins that might help stabilize these DNA structures, in vivo. To identify D. melanogaster sequence DNAs encoding dodeca-satellite binding proteins, we used the in vivo yeast assay, known as 'one-hybrid system'. Here, we identified a novel gene sequence that encoded pericentromeric dodeca-satellite binding protein and described its sequence characteristics.

Variability of DNA methylation pattern in somatic and germ cells in male newt (Amphibia, Urodela) Triturus cristatus carnifex.

In a survey of several mammalian genomes, namely humans, rodents and bovines, the differences in the 5-methylcytosine (m5C) content show that repeated DNA sequences from sperm were undermethylated and from various somatic tissues were heavily methylated. This report shows a pattern of methylation in male newt (Amphibia, Urodela) Triturus cristatus carnifex (T. c. c.) unlike that so far described by other authors in mammals. Using methylation sensitive and insensitive enzymes (HpaII and MspI) and successive 3' terminal labelling (fill-in), we found a greater degree of DNA methylation in premeiotic germ and sperm cells compared to somatic tissue such as hepatocytes. Furthermore the degree of total DNA methylation in spermatozoa appears somewhere between premeiotic germ cells and somatic tissue. Blot hybridization shows that two highly conserved repetitive sequences in amphibian T. c. c., pTvm1 and pTvm8, contribute significantly to the degree of DNA methylation, suggesting a function for these sequences, such as a role in transcriptional regulation.

Furan-mediated uncoupling of hepatic oxidative phosphorylation in Fischer-344 rats: an early event in cell death.

Furan is a potent rodent hepatotoxicant and carcinogen. The present study was done to examine the effects of furan on hepatic energy metabolism both in vivo and in vitro in male F-344 rats. Furan produced concentration- and incubation time-dependent irreversible reductions in ATP in freshly isolated F-344 rat hepatocytes. Furan-mediated depletion of ATP occurred prior to cell death and was prevented by including 1-phenylimidazole, a cytochrome P450 inhibitor, in the suspensions. Male F-344 rats were treated with furan (0-30 mg/kg, po) and killed 24 hr later to prepare hepatic mitochondria. Furan produced dose-dependent increases in state 4 respiration and ATPase activity. Both of these changes were prevented by 1-phenylimidazole cotreatment. In a separate series of experiments, mitochondria were prepared from isolated rat hepatocytes following incubation with furan (2-100 microM) for 1-4 hr. Furan produced incubation time- and concentration-dependent increases in state 4 respiration and ATPase activity. Furan-mediated mitochondrial changes were prevented by adding 1-phenylimidazole to the hepatocyte suspensions. These results indicate that the ene-dialdehyde metabolite of furan uncouples hepatic oxidative phosphorylation in vivo and in vitro. In vitro studies using an isolated hepatocyte suspension/culture system demonstrated that the concentration response for furan-mediated mitochondrial changes in suspension corresponded with the concentration responses for cell death after 24 hr. Including 1-phenylimidazole or oligomycin plus fructose in hepatocyte suspensions prevented furan-induced cell death after 24 hr in culture. The results of this study indicate that furan-induced uncoupling of oxidative phosphorylation is an early, critical event in cytolethality both in vivo and in vitro.

Effects of dialysis membrane on intradialytic vancomycin administration.

STUDY OBJECTIVE: To quantify the influence of hemodialyzers on vancomycin removal when the drug was infused during hemodialysis. DESIGN: Prospective, controlled, crossover study with three arms. SETTING: A university-affiliated medical center. PATIENTS: Eight subjects receiving outpatient hemodialysis. INTERVENTIONS: The three treatment arms were vancomycin 1000 mg infused after dialysis was completed (control), and the same dosages infused during the last hour of hemodialysis with a cellulose triacetate (CT) and a cellulose acetate (CA) hemodialyzer. MEASUREMENTS AND MAIN RESULTS: The areas under the curve from time zero to 44 hours (AUC0-44 hrs) for the three study arms were significantly different (p < 0.05), with the mean vancomycin AUC0-44 hrs being significantly lower when administered during CT and CA dialysis (73.7% and 87.2% of control; p < 0.05 vs control). The mean vancomycin peak concentration achieved during CT dialysis was significantly lower than for the CA and control arms (20.5, 23.9, 27.0 mg/L, respectively). Forty-four-hour postinfusion concentrations were similarly lower. CONCLUSION: Clinicians should recognize that the composition of the hemodialyzer significantly influences vancomycin serum concentrations when the drug is administered during hemodialysis.

Sex differences in rat hepatic cytolethality of the protein kinase C inhibitor safingol: role of biotransformation.

Safingol [(2S,3S)-2-amino-1,3-octadecanediol], a sphingosine analog that inhibits protein kinase C, was developed to treat dermatoses and cancer. Preclinical toxicology studies performed to assess the effects of safingol showed that 6 weeks of dermal application over 10% of body surface area caused dose-dependent increases in serum enzymes and hepatic histopathological changes associated with liver damage in female rats. Liver toxicity was not seen in male rats at the same doses. Plasma safingol concentrations were similar in male and female rats following topical exposure. The underlying mechanism(s) for the sex differences in toxicity in rats were examined using isolated hepatocytes. An in vitro model of male versus female differences in safingol.HCl-induced hepatotoxicity was established using a suspension/culture technique. Concentrations of safingol.HCl which produced cytolethality in 50% of the hepatocytes were 125 and 48 microM for male and female rat hepatocytes, respectively. Cytolethality was time-, concentration-, and cell number-dependent. Inhibition of cytochrome P450 in vitro with 1-phenylimidazole increased safingol.HCl-induced cytolethality in male but not female hepatocytes, suggesting that male rat hepatocytes have a cytochrome p450 isoenzyme which metabolizes safingol.HCl to an inactive metabolite thus reducing hepatotoxicity. Furthermore, in vivo pretreatment with the CYP4A-inducing agent, clofibrate, protected both male and female hepatocytes from cytolethality. The results of this study indicate that the sex differences seen in hepatotoxicity could be due to differences in biotransformation such that female rat hepatocytes either lack or have a reduced constitutive level of a cytochrome P450 isoenzyme that metabolizes safingol to a nontoxic metabolite. In addition, safingol produced hepatocyte cell death without inflammation in vivo, and a "ladder-like" DNA fragmentation pattern in vitro, consistent with an apoptotic mechanism of cell death.

Inhibition of ATPase activity in rat synaptic plasma membranes by simultaneous exposure to metals.

Inhibition of Na+/K+-ATPase and Mg2+-ATPase activities by in vitro exposure to Cd2+, Pb2+ and Mn2+ was investigated in rat brain synaptic plasma membranes (SPMs). Cd2+ and Pb2+ produced a larger maximal inhibition of Na+/K+-ATPase than of Mg2+-ATPase activity. Metal concentrations causing 50% inhibition of Na+/K+-ATPase activity (IC50 values) were Cd2+ (0.6 microM) < Pb2+ (2.1 microM) < Mn2+ (approximately 3 mM), and the former two metals were substantially more potent in inhibiting SPM versus synaptosomal Na+/K+-ATPase. Dixon plots of SPM data indicated that equilibrium binding of metals occurs at sites causing enzyme inhibition. In addition, IC50 values for SPM K+-dependent p-nitrophenylphosphatase inhibition followed the same order and were Cd2+ (0.4 microM) < Pb2+ (1.2 microM) < Mn2+ (300 microM). Simultaneous exposure to the combinations Cd2+/Mn2+ or Pb2+/Mn2+ inhibited SPM Na+/K+-ATPase activity synergistically (i.e., greater than the sum of the metal-induced inhibitions assayed separately), while Cd2+/Pb2+ caused additive inhibition. Simultaneous exposure to Cd2+/Pb2+ antagonistically inhibited Mg2+-ATPase activity while Cd2+/Mn2+ or Pb2+/Mn2+ additively inhibited Mg2+-ATPase activity at low Mn2+ concentrations, but inhibited antagonistically at higher concentrations. The similar IC50 values for Cd2+ and Pb2+ versus Mn2+ inhibition of Na+/K+-ATPase and the pattern of inhibition/activation upon exposure to two metals simultaneously support similar modes of interaction of Cd2+ and Pb2+ with this enzyme, in agreement with their chemical reactivities.

Falsely elevated serum vancomycin concentrations in hemodialysis patients.

Fluorescence polarization immunoassay (FPIA) is the most widely used clinical vancomycin assay in the United States. Questions exist regarding the accuracy of this polyclonal assay in patients with end-stage renal disease (ESRD). While several studies have reported discrepancies in vancomycin serum concentrations determined by FPIA compared with other vancomycin assays, no study has investigated the accuracy of vancomycin serum concentrations determined by FPIA in patients with ESRD undergoing maintenance hemodialysis. Therefore, we compared the assay performance of FPIA and enzyme multiplied immunoassay technique (EMIT) in six subjects with ESRD receiving high-efficiency hemodialysis. Subjects underwent 6 consecutive weeks of hemodialysis treatment with a cellulose acetate dialyzer (CA210) and received 1 g vancomycin intravenously once weekly during the last hour of dialysis. Vancomycin serum concentrations were determined by both EMIT and FPIA methodologies. From the serum concentration results of both assays, vancomycin dosing recommendations were calculated to achieve a desired steady-state peak concentration of 35 mg/L and trough concentration of 10 mg/L. Overall, vancomycin serum concentrations reported by FPIA were significantly higher than those reported by EMIT. The mean difference between assays in the peak serum concentrations at weeks 1, 4, and 6 was 7.5, 11.5, and 11.2 mg/L, respectively. The mean difference in trough serum concentrations at weeks 1, 4, and 6 was 4.2, 6.2, and 5.2 mg/L, respectively. The FPIA overestimation of the EMIT values (calculated as FPIA-EMIT) varied widely among study subjects with a range of 0.0 mg/L to 27.0 mg/L for peak serum concentrations and 0.0 mg/L to 12.8 mg/L for trough serum concentrations. The mean doses calculated based on FPIA results were significantly lower than the EMIT-derived doses. No significant difference was observed in the calculated dosing intervals. These results demonstrate that FPIA significantly overestimates vancomycin serum concentrations compared with EMIT in patients with ESRD undergoing high-efficiency hemodialysis. The overestimation by FPIA may result in significantly different vancomycin dosing recommendations, leading to underdosing and the potential for therapeutic failures. Due to the unpredictability of the overestimation by FPIA, we were unable to formulate vancomycin dosing guidelines for institutions that use FPIA. Therefore, we recommend that the EMIT vancomycin assay be used in patients with ESRD to ensure appropriate dosing.

Furan-induced cytolethality in isolated rat hepatocytes: correspondence with in vivo dosimetry.

Furan, a rodent hepatotoxicant and hepatocarcinogen, produced incubation time- and concentration-dependent decreases in the glutathione (GSH) content and viability of freshly isolated F-344 rat hepatocytes in vitro. Since furan itself did not significantly react with GSH, these data indicate the formation of a reactive metabolite of furan in hepatocyte suspensions. Treatment of the hepatocyte suspensions with the cytochrome P450 inhibitor 1-phenylimidazole delayed GSH depletion but did not alter furan-induced (4 to 12 mM) cytolethality. The furan concentrations required to produce measurable hepatocyte cytolethality in vitro within 6 hr (4 to 12 mM) were several orders of magnitude greater than the predicted maximal liver concentrations of furan in vivo following hepatotoxic doses. In order to study the mechanisms involved in the cytolethality of furan toward hepatocytes in vitro at concentrations relevant to hepatotoxicity in vivo, a hepatocyte suspension/culture system was developed that utilized furan concentrations and incubation times similar to hepatic dosimetry in vivo. Freshly isolated rat hepatocytes in suspension (in Williams' Medium E) were incubated with furan (2 to 100 microM) for 1-4 hr and placed in culture, and viability was determined after 24 hr by lactate dehydrogenase release. Furan produced cytolethality (5 to 70%) and modest GSH depletion in an incubation time- and concentration-dependent manner. Both GSH depletion and cytolethality induced by furan were prevented by 1-phenylimidazole and enhanced by acetone pretreatment of the rats. These data show that oxidation of furan by cytochrome P450 is required for GSH depletion and cytolethality, indicating that a reactive metabolite is involved in cell death. The results of this study underscore the importance of using in vivo toxicant concentrations and exposure times for in vitro mechanistic studies of chemically induced cytolethality.

Kinetic analysis of furan biotransformation by F-344 rats in vivo and in vitro.

Furan is both hepatotoxic and hepatocarcinogenic in rats. The kinetics of furan biotransformation by male F-344 rats were studied in vivo and in vitro in order to understand target tissue dosimetry. A physiologically based pharmacokinetic (PBPK) model for furan in rats was developed from gas uptake studies using initial furan concentrations of 100, 500, 1050, and 3850 ppm. Tissue partition coefficients for furan were determined in vitro using vial equilibration techniques. Furan gas uptake kinetics in vivo were described by a single saturable process with a Vmax of 27.0 mumol/hr/250 g rat and a KM of 2.0 microM. Furan metabolism in vivo was inhibited by pyrazole. The furan PBPK model adequately simulated blood and liver furan concentrations following 4-hr inhalation exposures to 52, 107, and 208 ppm furan. The biotransformation of furan was studied in freshly isolated rat hepatocytes in vitro and compared to biotransformation in vivo. Furan biotransformation by isolated rat hepatocytes exhibited a KM of 0.4 microM and a Vmax of 0.018 mumol/hr/10(6) cells. Inhibition and induction studies indicated that cytochrome P450 was the catalyst of furan oxidation. Acetone pretreatment of the rats produced a five-fold increase in the rate of the hepatocyte oxidation of furan, suggesting an important role for cytochrome P450 2E1. The Vmax determined in hepatocytes in vitro extrapolated to 23.0 mumol/hr/250 g rat, assuming 128 x 10(6) hepatocytes/g liver. Incorporation of the in vitro hepatocyte kinetic parameters into the PBPK model for furan accurately simulated in vivo pharmacokinetics. These results suggest that freshly isolated hepatocytes are a valuable in vitro system for predicting chemical pharmacokinetics in vivo.

Interaction of tricyclic drug analogs with synaptic plasma membranes: structure-mechanism relationships in inhibition of neuronal Na+/K(+)-ATPase activity.

Perturbations of rat brain synaptic plasma membrane (SPM) bilayer structure and Na+/K(+)-ATPase activity were correlated for drugs that are structurally related and exhibit similar toxicological side effects but belong to different pharmacological classes. Na+/K(+)-ATPase IC50 values decrease linearly with increasing octanol/water partition coefficients (log-log plot) for a series of dimethylethylamine-containing drugs (i.e., chlorpromazine, amitriptyline, imipramine, doxepin, and diphenhydramine), emphasizing hydrophobicity in inhibition. However, nortriptyline and desipramine are 1.2 log units less hydrophobic than their N-methylated parent drugs but more potent inhibitors. To investigate this, bilayer surface structure was examined by the binding of the fluorophore 1-anilinonaphthalene-8-sulfonic acid (ANS) to SPMs. The dissociation constant and wavelength maximum of ANS are invariant with drug binding; however, the limiting fluorescence intensity of ANS (F infinity) is increased. Such data indicate that these cationic drugs bind to the membrane surface, increasing the number but not the polarity of ANS binding sites by cancelling charge at anionic phospholipid groups. More importantly, there is a close linear correlation between the concentrations of drugs necessary to increase F infinity by 40% and the IC50 values, with full compensation for the N-demethylated drugs. This correlation implies that drug-induced increases in SPM-bound ANS fluorescence are a better predictor of Na+/K(+)-ATPase inhibition than are octanol/water partition coefficients and that electrostatic interactions are also involved in inhibition. Furthermore, it points toward similar mechanisms of biomembrane surface interaction governing both inhibition and fluorescence change that are common to these drugs. K(+)-dependent p-nitrophenylphosphatase activity is inhibited with the same potency as Na+/K(+)-ATPase activity, indicating that inhibition may involve drug interaction near the K+ binding sites. Furthermore, chlorpromazine, diphenhydramine, and dimethylaminopropyl chloride alter K(+)-activation of K(+)-dependent p-nitrophenylphosphatase, progressing from noncompetitive through mixed to competitive inhibition as their hydrophobicity changes, and these mechanisms are consistent with steric hindrance of K+ binding. In contrast to the ANS data, decreases in 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy induced by these drugs do not correlate with Na+/K(+)-ATPase inhibition, and drug N-demethylation enhances inhibition without altering anisotropy; both findings indicate that Na+/K(+)-ATPase activity is not predominantly influenced by changes in bulk fluidity. Taken together, these data suggest that electrostatic interactions at the biomembrane surface between the protonated amino group of the drug and anionic groups on the enzyme and/or phospholipids near the K+binding sites are crucial to inhibition and that drug hydrophobicity modulated the number and orientation of these interactions.

Induced crossing-over in Drosophila melanogaster germ cells of DNA repair-proficient and repair-deficient (mei-9L1) males following larval feeding with 5-azacytidine and mitomycin C.

The effects of 5-azacytidine (5-AZ) and mitomycin C (MMC), administered by larval feeding, on crossing-over were measured in Drosophila melanogaster male germ cells of a DNA repair-proficient and a repair-deficient (mei-9L1) strain. Both 5-AZ and MMC are effective inducers of male crossing-over. The estimated number of induced recombination events was higher in repair-proficient than in mei-9L1 males. The apparently lower sensitivity of mei-9L1 males to crossing-over induction may be the result of an incomplete crossing-over process.

Comparison of plasma, serum, and whole blood ethanol concentrations.

The differences in ethanol concentrations, as measured by direct injection gas chromatography, among plasma, serum, and whole blood from living human subjects are examined. The samples containing serum and the corresponding ones containing whole blood arrived at the laboratory as part of the same submission. The ratio of the concentration of ethanol in serum to that in plasma is 1.00 +/- 0.01:1 with a range of 0.98:1 to 1.04:1. The serum/whole blood ratio and plasma/whole blood ratio are both 1.12 +/- 0.02:1. The former has a range of 1.09:1 to 1.18:1 and the latter ranges from 1.09:1 to 1.17:1.

Effects of various metabolites on two phosphoglucomutase allozyme activities from Drosophila melanogaster.

The effects of various metabolites on the two most common phosphoglucomutase allozymes (PGMA and PGMB) in Drosophila melanogaster have been investigated in vitro. 2,3-Diphosphoglycerate (2,3DPG) inhibited PGMA and PGMB to the same degree in the presence of 25 microM glucose-1,6-diphosphate (G1,6P2). However a higher concentration of G1,6P2 partially reversed the inhibition of PGMA exerted by 2,3DPG, so that in the presence of 150 microM G1,6P2 the inhibition of PGMA was half that of PGMB at pH 6.0. Glycerol-3-phosphate (G3P) had no significant effect at pH 7.4 but exerted an activating effect at pH 6.0 which was more pronounced in the case of PGMB. ATP, citrate, and fructose-1, 6-diphosphate (F1,6P2) inhibited both PGMA and PGMB. The differences found in vitro between these two allozymes can have a significant impact on in vivo function and, therefore, on the maintenance of PGM polymorphism in experimental populations of D. melanogaster studied in the laboratory.

Properties of the two common electrophoretic variants of phosphoglucomutase in Drosophila melanogaster.

Phosphoglucomutase (PGM) of adult stage in Drosophilia melanogaster has been characterized by gel filtration, ion-exchange chromatography, and isoelectric focusing. The two common electrophoretic variants, PGMA and PGMB, differ with respect to their kinetic and stability parameters. PGMA is more thermostable than PGMB but shows the same pH optimum, equal dependence on Mg2+, and identical molecular weight. There is no significant kinetic difference between the two allozymes at the optimum pH values, but at pH 6.0 the Km value for glucose-1,6-diphosphate of PGMB is significantly higher than that of PGMA. This difference might explain the observed selective advantage of the PgmA allele in population studies.