Quantifying movement of multiple threatened species to inform adaptive management of environmental flows

There is a growing need for water managers to refine and optimise environmental flow strategies (e-flows) to balance water requirements for humans and nature. With increasing demands for freshwater and consequent declines in biodiversity, managers are faced with the problem of how to adaptively manage e-flows for multiple stakeholders and species whose flow requirements may overlap or vary. This study assessed the effectiveness of a regulated e-flow release strategy from a dam, aimed at providing movement opportunities and facilitating reproductive processes for multiple threatened species. Movements of 24 Mary River cod (Maccullochella mariensis), 20 Australian lungfish (Neoceratodus forsteri) and 13 Mary River turtle (Elusor macrurus) were quantified using acoustic telemetry over a three-year period. The influence of regulated e-flow releases, season, river depth, water temperature and rainfall on animal movements was assessed using Generalised linear mixed models (GLMMs). Models showed that hydraulic connectivity provided by both natural flows and regulated e-flow releases facilitated movement of all three species between pool habitats, throughout the year. Mary River turtles made extensive use of regulated e-flow releases when moving between habitats, whereas Mary River cod and Australian lungfish required additional natural rises in river height above the regulated e-flows to trigger movements. Significant movement activity was also recorded for cod and turtles during the dry season (winter and spring), broadly coinciding with breeding periods for these species. The effectiveness of, and potential improvements to, current e-flow strategies to sustain key life-history requirements of these species is discussed. Findings suggest a revised e-flow strategy with relatively minor increases in the magnitude of e-flow releases throughout winter and spring, would be effective in providing movement opportunities and supporting reproductive success for all three species. This study demonstrates that by quantifying movement behaviour in an e-flow context, ecological risk assessment frameworks can then be used to assess and provide for critical life-history requirements of multiple species within the context of a highly regulated system under increasing water use demands.

Cardiopulmonary exercise testing in severe osteoarthritis: a crossover comparison of four exercise modalities

Cardiopulmonary exercise testing is performed increasingly for cardiorespiratory fitness assessment and pre-operative risk stratification. Lower limb osteoarthritis is a common comorbidity in surgical patients, meaning traditional cycle ergometry-based cardiopulmonary exercise testing is difficult. The purpose of this study was to compare cardiopulmonary exercise testing variables and subjective responses in four different exercise modalities. In this crossover study, 15 patients with osteoarthritis scheduled for total hip or knee arthroplasty (mean (SD) age 68 (7) years; body mass index 31.4 (4.1) kg.m^-2 ) completed cardiopulmonary exercise testing on a treadmill, elliptical cross-trainer, cycle and arm ergometer. Mean (SD) peak oxygen consumption was 20-30% greater on the lower limb modalities (treadmill 21.5 (4.6) (p < 0.001); elliptical cross-trainer (21.2 (4.1) (p < 0.001); and cycle ergometer (19.4 (4.2) ml.min^-1 .kg^-1 (p = 0.001), respectively) than on the arm ergometer (15.7 (3.7) ml.min^-1 .kg^-1 ). Anaerobic threshold was 25-50% greater on the lower limb modalities (treadmill 13.5 (3.1) (p < 0.001); elliptical cross-trainer 14.6 (3.0) (p < 0.001); and cycle ergometer 10.7 (2.9) (p = 0.003)) compared with the arm ergometer (8.4 (1.7) ml.min^-1 .kg^-1 ). The median (95%CI) difference between pre-exercise and peak-exercise pain scores was greater for tests on the treadmill (2.0 (0.0-5.0) (p = 0.001); elliptical cross-trainer (3.0 (2.0-4.0) (p = 0.001); and cycle ergometer (3.0 (1.0-5.0) (p = 0.001)), compared with the arm ergometer (0.0 (0.0-1.0) (p = 0.406)). Despite greater peak exercise pain, cardiopulmonary exercise testing modalities utilising the lower limbs affected by osteoarthritis elicited higher peak oxygen consumption and anaerobic threshold values compared with arm ergometry.

Chemical immobilisation and satellite tagging of free-living southern cassowaries

BACKGROUND

The southern cassowary (Casuarius casuarius johnsonii) attains 1.8 m in height and over 80 kg in weight. These large birds are equipped with large claws and, although not a direct threat to humans, they have caused serious injury to handlers and members of the public.

METHODS AND RESULTS

This study describes chemical immobilisation, restraint, transport and post-monitoring (satellite tracking) methodologies for adult and juvenile southern cassowaries, captured and released from their natural environment.

CONCLUSIONS

The described methods have improved the management and research opportunities for the southern cassowary and may be transferable to other species of large ratite.

The autonomic control and functional significance of the changes in heart rate associated with air breathing in the jeju,Hoplerythrinus unitaeniatus

The jeju is a teleost fish with bimodal respiration that utilizes a modified swim bladder as an air-breathing organ (ABO). Like all air-breathing fish studied to date, jeju exhibit pronounced changes in heart rate(fH) during air-breathing events, and it is believed that these may facilitate oxygen uptake (MO2) from the ABO. The current study employed power spectral analysis (PSA) of fH patterns, coupled with instantaneous respirometry, to investigate the autonomic control of these phenomena and their functional significance for the efficacy of air breathing. The jeju obtained less than 5%of total MO2(MtO2) from air breathing in normoxia at 26°C, and PSA of beat-to-beat variability in fHrevealed a pattern similar to that of unimodal water-breathing fish. In deep aquatic hypoxia (water PO2=1 kPa) the jeju increased the frequency of air breathing (fAB) tenfold and maintained MtO2 unchanged from normoxia. This was associated with a significant increase in heart rate variability (HRV),each air breath (AB) being preceded by a brief bradycardia and then followed by a brief tachycardia. These fH changes are qualitatively similar to those associated with breathing in unimodal air-breathing vertebrates. Within 20 heartbeats after the AB, however, a beat-to-beat variability in fH typical of water-breathing fish was re-established. Pharmacological blockade revealed that both adrenergic and cholinergic tone increased simultaneously prior to each AB, and then decreased after it. However, modulation of inhibitory cholinergic tone was responsible for the major proportion of HRV, including the precise beat-to-beat modulation of fH around each AB. Pharmacological blockade of all variations in fH associated with air breathing in deep hypoxia did not, however, have a significant effect upon fAB or the regulation of MtO2. Thus, the functional significance of the profound HRV during air breathing remains a mystery.

A new method in applying power spectral statistics to examine cardio-respiratory interactions in fish

Power spectral analysis (PSA) provides a powerful tool for determining frequency oscillations in time signals, and it is accepted that mammals can show distinct components in the heart rate (fH) spectrum that are synchronous with ventilatory frequency (fV). Using similar signal processing techniques, these fundamental components at fV are not apparent in the spectrum calculated from fish fH. Here we compare conventional PSA on the R-R interval tachogram generated from ECG traces recorded in rats and fish, with PSA on the raw ECG waveform. The rat R-R tachogram showed a defined sigmoidal component, whereas the fish R-R tachogram was a more chaotic waveform. In agreement with the literature, PSA of these respective waveforms produced a component at the same frequency as ventilation in the rat, but of lower frequency than ventilation for the fish. Applying PSA to the rat ECG produced a spectrum with a fundamental component of similar frequency to that observed in the R-R tachogram spectrum, indicating that the latter adequately contained heart rate variability (HRV) oscillations. However, PSA of the ECG in fish contrasted with that from the R-R tachogram, with components observed in the latter spectrum being absent from the former. This suggests that the frequency components determined by PSA on the fish R-R tachogram were not true components, but were aliased (or folded-back) from higher up in the spectrum. Using established aliasing equations, recalculation of these peaks showed that their true frequency was similar to that of the ventilatory frequency for individual fish. The extent of cardio-respiratory interaction, resulting in fV < f(H/2) in rats but fV > f(H/2) in fish, is suggested to be the origin of the differences observed.

Shifts in a Fish’s Resource Holding Power during a Contact Paired Interaction: The Influence of a Copper‐Contaminated Diet in Rainbow Trout

The influence of sublethal chronic dietary copper (Cu) exposure on the dominant-subordinate relationship between pairs of juvenile rainbow trout (Oncorhynchus mykiss) was examined. Fish were fed either a normal (11 mg Cu kg(-1) food) or Cu-contaminated (721 mg Cu kg(-1) food) diet for 8 wk. Paired interactions were observed--control versus control, Cu-exposed versus Cu-exposed, and control versus Cu-exposed fish--using a computer-aided video tracking system to measure duration of interactions, total distance moved, and the number of encounters during each contest. In concurrence with game theory, each interaction became escalated with a lesser size disparity between contestants. However, in Cu-exposed versus Cu-exposed fish interactions, the dominant-subordinate relationship was decided sooner and with less aggression than a control versus control fish interaction with fish of a similar relative body mass disparity. During control versus Cu-exposed fish interactions, control fish would normally dominate interactions (12 out of 16 bouts) unless the Cu-exposed fish had a 15% body mass advantage. Muscle glycogen and lactate levels after each contest reflected the duration of bouts and winners of the contests, irrespective of Cu exposure. We conclude that Cu-contaminated fish are less able to compete and have lower resource holding power than controls and will withdraw from a contest at a lower level of interaction, unless a size advantage in the Cu-exposed fish increases the probability of winning.

The use of power spectral analysis to determine cardiorespiratory control in the short-horned sculpinMyoxocephalus scorpius

Anaesthesia and minor surgery to place electrocardiogram recording electrodes in the short-horned sculpin caused a decrease in mean normal beat(R–R) interval and heart rate variability (HRV), measured as the standard deviation in the R–R interval (SDRR). Mean R–R interval increased to a steady state value (1.9±2.9 s) 72 h post-surgery, but SDRR took 120 h to stabilise (0.56±0.09 s). Power spectral analysis applied to recordings of instantaneous heart rate showed no spectral peaks immediately after surgery, with the development of twin peaks (at 0.02 and 0.05 Hz) that also became stable 120 h post surgery. Bilateral cardiac vagotomy abolished the variability in beat-to-beat interval, and both the high and low frequency peaks, suggesting that much of the regulation of heart rate and HRV in sculpin was under parasympathetic, cholinergic control that was withdrawn as a result of surgical and handling stress. Rate of oxygen consumption \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(({\dot{M}}_{\mathrm{O}_{2}})\) \end{document} and heart rate (fH) were monitored simultaneously and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({\dot{M}}_{\mathrm{O}_{2}}\) \end{document} showed a good correlation with both mean R–R interval(r2=–0.89) and SDRR (r2=0.93),although a more significant (ANCOVA, P=0.02) covariance existed between the post-surgical decrease in \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({\dot{M}}_{\mathrm{O}_{2}}\) \end{document} and increase in SDRR. These data suggest that sculpin use fHas a way of moderating oxygen consumption, fine-tuned on a beat-to-beat basis by cholinergic control. We conclude that power spectral analysis is a useful method of determining HRV in fish, and that HRV is a more sensitive measure of recovery from disturbance than fH alone.

The CTP:phosphocholine cytidylyltransferase encoded by the licC gene of Streptococcus pneumoniae: cloning, expression, purification, and characterization

Streptococcus pneumoniae is a member of a small group of bacteria that display phosphocholine on the cell surface, covalently attached to the sugar groups of teichoic acid and lipoteichoic acid. The putative pathway for this phosphocholine decoration is, in its first two enzymes, functionally similar to the CDP-choline pathway used for phosphatidylcholine biosynthesis in eukaryotes. We show that the licC gene encodes a functional CTP:phosphocholine cytidylyltransferase (CCT). The enzyme has been expressed and purified to homogeneity. Assay conditions were optimized, particularly with respect to linearity with time, pH, Mg(2+), and ammonium sulfate concentration. The pure enzyme has K(M) values of 890+/-240 microM for CTP, and 390+/-170 microM for phosphocholine. The k(cat) is 17.5+/-4.0 s(-1). S. pneumoniae CTP:phosphocholine cytidylyltransferase (SpCCT) is specific for CTP or dCTP as the nucleotide substrate. SpCCT is strongly inhibited by Ca(2+). The IC(50) values for recombinant and native SpCCT are 0.32+/-0.04 and 0.27+/-0.03 mM respectively. The enzyme is also inhibited by all other tested divalent cations, including Mg(2+) at high concentrations. The cloning and expression of this enzyme sets the stage for design of inhibitors as possible antipneumococcal drugs.

Negative cooperativity of substrate binding but not enzyme activity in wild-type and mutant forms of CTP:glycerol-3-phosphate cytidylyltransferase

CTP:glycerol-3-phosphate cytidylyltransferase (GCT) catalyzes the synthesis of CDP-glycerol for teichoic acid biosynthesis in certain Gram-positive bacteria. This enzyme is a model for a cytidylyltransferase family that includes the enzymes that synthesize CDP-choline and CDP-ethanolamine for phosphatidylcholine and phosphatidylethanolamine biosynthesis. We have used quenching of intrinsic tryptophan fluorescence to measure binding affinities of substrates to the GCT from Bacillus subtilis. Binding of either CTP or glycerol-3-phosphate to GCT was biphasic, with two binding constants of about 0.1-0.3 and 20-40 microm for each substrate. The stoichiometry of binding was 2 molecules of substrate/enzyme dimer, so the two binding constants represented distinctly different affinities of the enzyme for the first and second molecule of each substrate. The biphasic nature of binding was observed with the wild-type GCT as well as with several mutants with altered Km or kcat values. This negative cooperativity of binding was also seen when a catalytically defective mutant was saturated with two molecules of CTP and then titrated with glycerol-3-phosphate. Despite the pronounced negative cooperativity of substrate binding, negative cooperativity of enzyme activity was not observed. These data support a mechanism in which catalysis occurs only when the enzyme is fully loaded with 2 molecules of each substrate/enzyme dimer.

Enzymatic and cellular characterization of a catalytic fragment of CTP:phosphocholine cytidylyltransferase alpha

To probe the mechanism of lipid activation of CTP:phosphocholine cytidylyltransferase (CCTalpha), we have characterized a catalytic fragment of the enzyme that lacks the membrane-binding segment. The kinetic properties of the purified fragment, CCTalpha236, were characterized, as well as the effects of expressing the fragment in cultured cells. CCTalpha236 was truncated after residue 236, which corresponds to the end of the highly conserved catalytic domain. The activity of purified CCTalpha236 was independent of lipids and about 50-fold higher than the activity of wild-type CCTalpha assayed in the absence of lipids, supporting a model in which the membrane-binding segment functions as an inhibitor of the catalytic domain. The kcat/Km values for CCTalpha236 were only slightly lower than those for lipid-activated CCTalpha. The importance of the membrane-binding segment in vivo was tested by expression of CCTalpha236 in CHO58 cells, a cell line that is temperature-sensitive for growth and CCTalpha activity. Expression of wild-type CCTalpha in these cells complemented the defective growth phenotype when the cells were cultured in complete or delipidated fetal bovine serum. Expression of CCTalpha236, however, did not complement the growth phenotype in the absence of serum lipids. These cells were capable of making phosphatidylcholine in the delipidated medium, so the inability of the cells to grow was not due to defective phosphatidylcholine synthesis. Supplementation of the delipidated medium with an unsaturated fatty acid allowed growth of CHO58 cells expressing CCTalpha236. These results indicate that the membrane-binding segment of CCTalpha has an important role in cellular lipid metabolism.

STEREO: a program on a PC-Windows 95 platform for recording and evaluating quantitative stereologic investigations of multistage hepatocarcinogenesis in rodents

The most common organ site of neoplasms induced by carcinogenic chemicals in the rodent bioassay is the liver. The development of cancer in rodent liver is a multistage process involving sequentially the stages of initiation, promotion, and progression. During the stages of promotion and progression, numerous lesions termed altered hepatic foci (AHF) develop. STEREO was developed for the purpose of efficient and accurate quantitation of AHF and related lesions in experimental and test rodents. The system utilized is equipped with a microcomputer (IBM-compatible PC running Windows 95) and a Summagraphics MICROGRID or SummaSketch tablet digitizer. The program records information from digitization of single or serial sections obtained randomly from rat liver tissue. With this information and the methods of quantitative stereology, both the number and volume percentage fraction of AHF in liver are calculated in three dimensions. The recorded data files can be printed graphically or in the format of tabular numerical data. The results of stereologic calculations are stored on floppy disks and can be sorted into different categories and analyzed or displayed with the use of statistics and graphic functions built into the overall program. Results may also be exported into Microsoft Excel for use at a later time. Any IBM-compatible PC capable of utilizing Windows 95 and MS Office can be used with STEREO, which offers inexpensive, easily operated software to obtain three-dimensional information from sections of two dimensions for the identification and relative potency of initiators, promoters, and progressors, and for the establishment of information potentially useful in developing estimations of risk for human cancer.

Quantitative stereological studies of a 'selection' protocol of hepatocarcinogenesis following initiation in neonatal male and female rats

A modified initiation-selection procedure for neonatal male and female rat hepatocarcinogenesis were examined utilizing the methods of quantitative stereology. In this study, diethylnitrosamine (10 mg DEN/kg) was given a few days after birth. At weaning, the rats were fed 0.02% 2-acetylaminofluorene (AAF) for 2 weeks with a mitotic stimulus [70% partial hepatectomy (PH)] after 1 week on the diet. Quantitative stereological analyses in conjunction with the use of several enzyme markers were used to determine the number and volume of altered hepatic foci (AHF) detected at 1 week, 3 months and 7 months after the selection procedure. This format resulted in an equivalent number of AHF in male and female rats. The AHF were three times larger in males than in females 1 week after discontinuation of AAF administration. Three months after the selection procedure, the number of AHF had decreased by at least a third and their volume percentage was the same in male and female rats. After 7 months, the number and volume fraction of detectable AHF in females were comparable to those which had been observed at 1 week after selection. In the male, the number but not the volume fraction were similar at 7 months compared with 1 week after selection. Both initiation with DEN and selection with AAF/PH contribute independently to the total population of AHF in male and female rats. At least half of the AHF detected 7 months after the selection protocol were due to DEN administration alone. Rats receiving only the AAF/PH selection exhibited one third of the number of AHF observed with the complete protocol. Administration of a non-necrogenic dose of DEN to neonatal rats when coupled with the AAF/PH selection procedure resulted in a significant promotion of the growth of initiated hepatocytes at 1 week, 3 months or 7 months after the selection procedure. These studies demonstrated that (i) the number of AHF detected after a non-necrogenic dose of DEN during the first week of life with subsequent AAF/PH selection after weaning decreases within the first 3 months after the selection procedure, but can re-develop with a promotion stimulus; (ii) the AAF/PH selection procedure itself may initiate hepatocytes in the absence of DEN administration; (iii) the AAF/PH selection procedure is equally effective with respect to the number of AHF observed after phenobarbital promotion in weaning male and female rats initiated near birth.

Focal and non-focal hepatic expression of placental glutathione S-transferase in carcinogen-treated rats

Carcinogenesis develops in stages that have been operationally defined as initiation, promotion and progression. Although morphological end points have been described for detection and quantitation of these stages, to date initiation has been assessed only in the context of clonal growth in response to certain promoting agents. Initiated cells are morphologically indistinguishable from surrounding cells and early changes at the cellular level during initiation have not been clarified. One commonly used end point for the detection of preneoplastic hepatic lesions i their aberrant expression of the placental isozyme of glutathione S-transferase (PGST). Because single hepatocytes expressing PGST have been detected in aged rats and in those administered hepatocarcinogens, it has been suggested that such cells constitute a population of putatively initiated hepatocytes. In order to further elucidate the characteristics of single PGST-positive hepatocytes, we analyzed the number of these cells 2 and 18 weeks after various doses (0-100 mg/kg) of diethylnitrosamine (DEN) and of dimethylbenz[a]anthracene (DMBA). When determined 14 days after carcinogen administration, the number of single hepatocytes expressing PGST was greater after DEN administration (ranging from 0.8 +/- 0.3 per cm2 transection of liver at 1 mg/kg to 33.0 +/- 4.7 at 100 mg/kg) than after DMBA administration (ranging from 0.25 +/- 0.14 at 10 mg/kg to 3.03 +/- 0.5 at 100 mg/kg); none were detected in control rats of the same age. Additional rats were maintained on a basal diet or a basal diet plus phenobarbital for a further 4 month period. Whereas individual PGST-positive hepatocytes were only sporadically detected in rats treated with DMBA and maintained on a basal diet for 18 weeks, those rats placed on phenobarbital for 16 weeks had an even higher number of such PGST-positive hepatocytes than at 2 weeks after DMBA administration. In contrast, the dose-response curve observed for DEN-treated rats 18 weeks after carcinogen administration was similar to that observed 2 weeks after carcinogen treatment for both phenobarbital- and non-phenobarbital-treated rats. In addition, the number of single PGST-positive hepatocytes detected at 2 weeks was directly parallel to the number of altered hepatic foci expressing PGST 18 weeks after DEN administration. The dose-dependent induction of PGST-positive single hepatocytes after treatment with two hepatocarcinogens, the dose-dependent growth of altered hepatic foci (AHF) expressing PGST with phenobarbital administration and the parallel dose-response curve of single hepatocytes expressing PGST and later of AHF expressing PGST argue strongly for a precursor role of single PGST-positive cells in the development of AHF expressing PGST.

Characterization of the promotion of altered hepatic foci by 2,3,7,8-tetrachlorodibenzo-p-dioxin in the female rat

Previous studies have suggested that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) acts as a promoting agent in various organ systems including the rat liver. Since a major characteristic of the stage of tumor promotion is its operational reversibility, we have assessed whether TCDD-induced promotion is reversible in a two-stage model of hepatocarcinogenesis. In this model, female Fischer F344 rats were administered a single, intragastric dose of the initiating agent, diethylnitrosamine (DEN, 10 mg/kg), at the peak of proliferation induced by a partial hepatectomy. TCDD was then administered biweekly (0.14 micrograms/kg, s.c.) for 1, 3 or 5 months. One group of animals was killed at each of these time points, while a second group was maintained for each time point for an additional 6 months in the absence of further TCDD. Four serial frozen sections of liver were each stained with a different enzyme marker of altered hepatic foci (AHF). The AHF were identified and the number and volume fraction determined by quantitative stereology. Exposure to TCDD resulted in an increase in the number and size of AHF in the initiated relative to the uninitiated rats. Increasing the duration of promotion with TCDD led to an increase in the number of AHF per liver, the volume fraction of the liver occupied by AHF and the number of markers expressed aberrantly by a single AHF. Discontinuation of TCDD administration for 6 months before killing the animals resulted in a decrease in the total number of AHF observed, but those AHF that remained increased in size with an overall increase in volume fraction of AHF. Analysis of the size class distribution for AHF for each of the periods of TCDD promotion revealed an increase in the larger AHF but a decrease in the smaller, thereby resulting in an overall decrease in number of AHF with an increase in the volume fraction of AHF. Increasing the duration of the TCDD exposure prior to its withdrawal led to an increased AHF size, phenotypic complexity and number of AHF remaining after cessation of TCDD administration. Although the levels of TCDD in livers of rats 6 months after cessation of TCDD administration were still greater than background, they were markedly reduced compared to immediately after administration. Thus, cessation of exposure to TCDD after a brief duration led to a reversal of its promotional effects on the majority of AHF, while prolonged exposure led to maintained promotion of a minority of AHF.

An initiation-promotion assay in rat liver as a potential complement to the 2-year carcinogenesis bioassay

Several pharmaceutical agents, manufacturing chemicals, and environmental contaminants were found to act primarily as promoting agents in an initiation-promotion paradigm. The phenotypic distribution of four enzyme markers--placental glutathione-S-transferase (PGST), gamma-glutamyl transpeptidase (GGT), canalicular ATPase (ATPase), and glucose-6-phosphatase (G6Pase)--was analyzed in altered hepatic foci (AHF) by quantitative stereology. The number and volume distribution of AHF were determined for each promoter tested. For phenobarbital and 2,3,7,8-tetrachloro-p-dioxin, PGST and GGT together scored 100% of the AHF; for 1-(phenylazo)-2-naphthol (CI solvent yellow 14) and chlorendic acid, PGST alone marked 90% of the AHF; after chronic administration of WY-14,643, ATP and G6Pase were the predominant markers. In rats fed tamoxifen, G6P scored more than half of the AHF. Differences in the number of AHF promoted by each of these agents and in their phenotypic distributions may reflect the differentially responsive nature of individual initiated hepatocytes to the action of specific promoters. Since the chronic bioassay of suspected carcinogens does not allow one to differentiate between weak complete carcinogens and those carcinogenic agents that act in a reversible manner to promote the growth of previously initiated cells, the partial hepatectomy, altered-hepatic-focus model of cancer development is proposed as a supplement to the chronic bioassay for the identification of those carcinogenic agents that are primarily, if not exclusively, promoting agents in rat liver.

Quantitative stereological analysis of the effects of age and sex on multistage hepatocarcinogenesis in the rat by use of four cytochemical markers

Altered hepatic foci (AHF) were analyzed by quantitative stereology on frozen serial sections stained sequentially for gamma-glutamyltranspeptidase (GGT), canalicular adenosine triphosphate (ATPase), glucose-6-phosphatase (G6Pase), and the placental isoenzyme of glutathione S-transferase (GST). Livers for these analyses were obtained from both male and female rats of different ages which had been subjected to initiation with a nonnecrogenic dose of diethylnitrosamine following a 70% partial hepatectomy with subsequent phenobarbital (PB) feeding. Different combinations of these four marker alterations (from single marker to four-marker combinations) were used to analyze the data, and the results were compared for their ability to detect AHF. In rats on the above protocol, GST was the single most effective marker, exhibiting a high sensitivity for scoring both number and volume of foci. There was a high degree of overlap with GGT. The combination of the four different markers, GST/GGT/ATPase/G6Pase, scored 80% more foci in number and 60% more in volume than the routinely used GGT/ATPase/G6Pase method. When all four markers were used to score AHF, PB promotion was equally effective in both sexes at weaning and at 6 months of age, but at 1 year of age males showed a dramatic reduction in the effectiveness of PB as a promoting agent, both for number and volume percentage of liver occupied by AHF. On the other hand, initiation was more effective in the male at weaning and at 6 months of age, although by the 12-month point no distinction between the sexes could be made. When only GGT was used as a marker, promotion by PB appeared to be markedly less effective in males than in females at all ages. In the absence of PB administration, both the number and volume fraction of AHF in the livers of both males and female increased with age. Likewise, both the number of AHF per liver and their volume fractions increased with age in both sexes when uninitiated animals were fed PB, although only after a 6-month lag in females. These experiments demonstrate that the stages of initiation and promotion in hepatocarcinogenesis in the rat as monitored by the number and volume percentage occupied of AHF are altered by both the age and the sex of the animal. The combination of GGT and GST identified all AHF scored by the GST/GGT/ATPase/G6Pase set of markers and thus may be the most efficient combination of markers of AHF resulting from promotion by PB.

Critical parameters in the quantitation of the stages of initiation, promotion, and progression in one model of hepatocarcinogenesis in the rat

Critical parameters in the quantitation of altered hepatic foci (AHF) developing during multistage hepatocarcinogenesis in the rat include: 1) the enumeration of AHF induced by test agents as well as those AHF occurring spontaneously in livers of untreated animals; 2) the volume percentage or fraction of the liver occupied by all AHF as a reflection of the total number of altered cells within the liver and the degree of tumor promotion which has occurred; and 3) the phenotype of individual AHF as determined by multiple markers with serial sections. These parameters, especially the number of AHF, should be corrected by the presence of spontaneous AHF which increase with the age of the animal, more so in males than females. While accurate estimation of the background level of spontaneous AHF can be important in demonstrating that a carcinogenic agent does not possess the ability to increase the numbers of AHF above the background level, a better method to distinguish the effectiveness and relative potencies of agents as initiators or promoters is reviewed. The relative effectiveness of four different markers--gamma-glutamyltranspeptidase (GGT), a placental form of glutathione S-transferase (GST), canalicular ATPase, and glucose 6-phosphatase (G6Pase)--was described for the chemicals C.I. Solvent Yellow 14 and chlorendic acid as promoting agents in males and females. C.I. Solvent Yellow 14 is a more effective promoting agent in females than males, and AHF exhibit extremely low numbers scored by GGT. On the other hand, the numbers of AHF present in livers of male rats promoted by this agent are more than twice those seen in livers of female animals, possibly owing to the effectiveness of this agent as an initiator in the male but not the female. Very few AHF, especially in the male, are scored by GGT during chlorendic acid promotion. The distribution of phenotypes with these markers also differs in the spontaneous AHF appearing in the livers of animals fed 0.05% phenobarbital on either a crude NIH-07 or AIN-76 purified diet. Such studies emphasize the extreme dependence of the promoting stage of hepatocarcinogenesis on environmental factors of sex, diet, and the molecular nature of the promoting agent itself. The hallmark of the final stage of progression in the development of hepatocellular carcinomas is aneuploidy, which may be reflected by phenotypic heterogeneity within individual AHF, termed foci-in-foci. The implications of such quantitative analyses during hepatocarcinogenesis induced by specific agents in relation to the specific action of the agent at one or more of the stages of hepatocarcinogenesis are discussed.

An approach to the determination of the relative potencies of chemical agents during the stages of initiation and promotion in multistage hepatocarcinogenesis in the rat

The potency of carcinogenic agents in eliciting neoplastic lesions has long been a concern of investigators in the field of oncology. This paper describes a method, based on quantitative stereologic calculations, to estimate the relative potency of chemicals as initiating and/or promoting agents. The parameters defined in this paper are: (a) Initiation index = no. foci induced X liver-1 X [mmole/kg body weight]-1; and (b) Promotion index = Vf/Vc X mmol-1 X wk-1. These parameters have been calculated for a number of chemical agents, based both on data from this laboratory and others published in the literature. Neither parameter varied significantly with the dose of two different initiating agents used in this study. The range of promotion indices extended over more than eight orders of magnitude, whereas that of the initiation indices was much less variable. Such parameters may be useful as quantitative estimates of the potency of hepatocarcinogenic agents not only in rodents, but potentially in quantitative risk estimations in the human.

A method to quantitate the relative initiating and promoting potencies of hepatocarcinogenic agents in their dose-response relationships to altered hepatic foci

The relative response to various initiating doses of diethylnitrosamine (DEN) and dimethylbenz[a]anthracene of the induction of numbers and size (vol. % of liver) of altered hepatic foci (AHF) in livers of adult female rats of the Sprague-Dawley and Fischer 344 (F-344) strains was studied by methods of quantitative stereology in the presence and absence of the promoting agent, phenobarbital (PB, 0.05% in the diet). In all cases, a relatively linear response with dose, even at the lowest doses employed, was obtained except for the numbers of AHF at the highest dose of DEN (30 mg/kg), which was not significantly different from that at a dose of 10 mg/kg in F-344 female rats. Similar dose-response data were obtained at various doses of two promoting agents effective in hepatocarcinogenesis, PB and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), in livers of F-344 female rats following initiation with DEN (10 mg/kg) 24 h post-70% hepatectomy. The response to these agents exhibited threshold levels below which no increase in number or vol. % of liver of AHF was noted in comparison with that in livers of animals not treated with the promoting agents. At several subthreshold doses of both PB and TCDD an inhibition of AHF formation and growth (measured as vol. % of liver) was observed. Based on quantitative stereologic calculations, parameters for the estimation for the relative potency of chemicals as initiating or promoting agents have been established. These are defined as: initiation index = no. of foci induced X liver-1 X [mmol/kg body wt]-1 and promotion index = Vf/Vc X mmol-1 X weeks-1, where Vf is the total volume fraction (%) occupied by AHF in the livers of rats treated with the test agent and Vc is the total volume of AHF in control animals which have only been initiated. These parameters were calculated for a number of agents based on data published in the literature and from those reported herein. Neither parameter varied significantly with the dose of the initiating agent based on the data in this paper. The range of promotion indices extended over more than eight orders of magnitude, whereas that of initiation indices was much less variable. Such parameters may be useful as quantitative estimates of the potency of hepatocarcinogenic agents, such values having potential application to risk estimations.

Quantitative stereological evaluation of four histochemical markers of altered foci in multistage hepatocarcinogenesis in the rat

Female F344/N rats dosed with diethylnitrosamine (DEN) 24 h after partial hepatectomy were treated with the promoting agents, phenobarbital (PB) or 3,4,7,8-tetrachlorodibenzo-p-dioxin (TCDD), or the peroxisome proliferating agent, WY 14,643, for 6 months. Another group was subjected to the Solt-Farber protocol. Altered hepatic foci (AHF) were analyzed by quantitative stereology from frozen serial sections stained for gamma-glutamyl transferase (GGT), canalicular adenosine triphosphatase (ATPase), glucose-6-phosphatase (G6Pase) and the placental isozyme of glutathione S-transferase (PGST). PGST scored more foci in all groups than GGT and ATPase. PGST marked greater focal volume than GGT or ATPase, and PGST marked focal volume equal to or greater than G6Pase in rats treated with PB, TCDD or the Solt-Farber protocol. However, after treatment with WY 14,643, GGT and PGST marked much less focal volume than ATPase or G6Pase, and PGST scored fewer foci than G6Pase. Numerical estimations of foci scored by those markers on the basis of area of the entire tissue section (per cm2) were relatively different from those values determined by quantitative stereology. While these results confirm earlier studies, they demonstrate the importance of quantitative stereologic analysis of AHF during multistage hepatocarcinogenesis.

Application of quantitative stereology to the evaluation of phenotypically heterogeneous enzyme-altered foci in the rat liver

Quantitative stereologic relationships are applied in this report to the evaluation of F344 rat liver foci where the tissue sections exhibit congruent enzyme-altered areas of the several different phenotypes as well as enzyme-altered areas within a larger area of another enzyme alteration, that is, a "focus within a focus.' Quantitation of both the numbers and volume occupied by each of the phenotypes of the enzyme-altered foci was accomplished by the unique logic described in this report. The application of this logic to four representative experimental protocols with the use of three phenotypic markers demonstrated all possible congruent phenotypes as well as a small number of "foci within foci.' The variance of the quantitation of the experimental data was shown to depend on the number of focal transections identified in the sections, the number of sections examined, and the distribution of phenotypic alterations among foci.

Enhancement of hepatocarcinogenesis in female rats by ethinyl estradiol and mestranol but not estradiol

The effect of dietary exposure to synthetic estrogens on hepatocarcinogenesis was evaluated. Diethylnitrosamine-initiated and 0.85% NaCl solution-treated noninitiated female Sprague-Dawley rats were transferred to semisynthetic diets containing mestranol (0, 0.1, or 0.5 ppm), ethinyl estradiol (0.5 ppm), estradiol (0.6 ppm), or mestranol plus beta-methasone (0.5 and 0.2 ppm, respectively). gamma-Glutamyl transferase (GGT)-positive transections and hematoxylin and eosin-detectable nodules and carcinomas were scored at 9 and 12 months. Quantitative stereological calculations were performed to determine GGT lesion number and size. At 9 months, in diethylnitrosamine-initiated rats, ethinyl estradiol and mestranol caused 3.5- and 4.4-fold increases, respectively, in the number of GGT lesions per liver and an increased incidence of hepatocellular carcinomas while estradiol had no enhancing effect. Addition of beta-methasone to the mestranol-containing diet caused a significant decrease in GGT lesion number but not carcinoma incidence compared to mestranol alone. At 12 months, in diethylnitrosamine-initiated rats, mestranol caused a dose-dependent increase in GGT lesion number. The hepatocellular carcinoma incidence was significantly increased at the high mestranol dose. Small increases in the numbers of larger GGT lesions were also observed in noninitiated animals treated with mestranol and ethinyl estradiol and are most probably due to promotion of spontaneously initiated hepatocytes. These results indicated that the synthetic estrogens cause dramatic increases in the number of presumptive preneoplastic GGT lesions. Carcinoma incidence is also enhanced. Thus, these results confirm and extend our previous studies which together with the results of others have shown that synthetic estrogens can act as promoters of hepatocarcinogenesis.

The natural history and dose-response characteristics of enzyme-altered foci in rat liver following phenobarbital and diethylnitrosamine administration

Enzyme-altered foci (EAF) were induced in the liver of female rats by 70% partial hepatectomy (PH), followed by a single intragastric administration of diethylnitrosamine (DEN) at a dose of 10 mg/kg. The stability and response of these foci to various doses of the hepatic promoting agent, phenobarbital (PB), were studied. The number of gamma-glutamyltranspeptidase-positive (GGT+) EAF resulting from PH/DEN followed by PB (0.05%) administration for 1 week, 2 weeks, 1 month, 2 months, 3 months or 4 months did not significantly change when the administration of the promoting agent was followed by a 6-month period of a diet containing no PB. These data demonstrate the stability of the foci induced by the PH/DEN/PB regimen and indicate that the increased number of foci resulting from PB promotion in the absence of overt hepatic necrosis are not reversible on removal of the promoting stimulus. Chronic administration of dose levels of PB below 0.001% in the diet failed to demonstrate an increase in the number of EAF over the number in the control animals not promoted with PB. A linear increase in the number of EAF was observed when rats were chronically fed doses of PB ranging between 0.001% and 0.05% in the diet, whereas diet concentrations of PB greater than 0.05% did not result in any further increase in the number of EAF. The number of EAF resulting from PH/DEN followed by 0.05% PB in the diet increased during the first 3-4 months of promotion. Thereafter, the number of foci did not change despite the continued administration of PB for as long as 8 months. These data suggest the presence of an apparent threshold (no effect level) for promotion by PB and demonstrate the presence of a maximal response of EAF to this promoting agent after initiation by a single dose of DEN.

Effects of hormones and amino acid depletion on the kinetic parameters of amino acid uptake in monolayer cultures of rat hepatocytes

Uptake of 2-aminoisobutyric acid (AIB) at concentrations of 0.1 mM to 30 mM was examined in sodium-containing and sodium-free media in hepatocytes pretreated without hormones (control), with hormones, or with amino acid depletion. Results show that 1-minute but not 4-minute rates can be taken as initial rates for the total or sodium-dependent transport of AIB. The data for the 1-minute sodium-dependent transport of AIB were analyzed by a computer program and also by Eadie-Hofstee and Lineweaver-Burk plots, and a single saturable system was found. In the control cultures, the saturable system had a Km of 1-2 mM AIB and a Vmax of 1.2 nmoles AIB/mg protein/minute. There was an increase in the Vmax of two to three-fold after pretreating the cultures with insulin or amino acid depletion, three to four-fold with glucagon, and six to seven fold with glucagon + dexamethasone.

Application of quantitative stereology to the evaluation of enzyme-altered foci in rat liver

The mathematical science of quantitative stereology has established relationships for the quantitation of elements in three-dimensional space from observations on two-dimensional planes. This report describes the utilization and importance of such mathematical relationships for the quantitative analysis of focal hepatic lesions in terms relative to the volume of the liver. Three examples are utilized to demonstrate the utility of such calculations in the three-dimensional quantitation of hepatic focal lesions. The first is that of a computer-simulated experiment based on defined hypothetical situations. The simulations demonstrate the applicability of the computations described in this report to the evaluation of two-dimensional data from typical animal experiments. The other two examples are taken from actual experiments and involve the transplantation of hepatic cell populations into the liver suitably prepared hosts and the quantitation of altered foci produced by initiation with diethylnitrosamine-partial hepatectomy followed by promotion with phenobarbital. The quantitation of altered foci by means of a two-dimensional analysis (simple enumeration of focal intersections/area of tissue section) is proportional to the quantitation of foci per volume of liver provided that the mean diameter of the foci for each treatment is sufficiently uniform, as exemplified in the text by the transplantation experiment. When such mean diameters are unequal as in the diethylnitrosamine-phenobarbital experiment described herein, quantitation from three-dimensional analysis gives significantly different results as compared with enumeration of focal intersections on two-dimensional areas. These studies clearly demonstrate that the frequency and size of foci intersections viewed on two-dimensional tissue sections do not necessarily reflect the number of size of foci in the three-dimensional tissue. Only by quantitating the number and size of the foci in relation to the three-dimensional volume of the tissue can one determine the validity of the proportionality of data from two-dimensional measurements to the total number of foci per volume of tissue. Such a conclusion has important implications for quantitative studies on hepatocarcinogenesis as well as for the enumeration of premalignant lesions which occur during the natural history of carcinogenesis in any solid tissue.

Quantitative evaluation of the promotion by 2,3,7,8-tetrachlorodibenzo-p-dioxin of hepatocarcinogenesis from diethylnitrosamine

In order to test the potential of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as a promoter of hepatocarcinogenesis, rats which had received a single 10-mg/kg dose of diethylnitrosamine (DEN) following partial hepatectomy were given TCDD (0.14 and 1.4 micrograms/kg s.c. once every 2 weeks) for 7 months. Animals which received (a) only a single initiating dose of DEN after partial hepatectomy and no further treatment of (b) TCDD alone with no initiating dose of DEN exhibited relatively few enzyme-altered foci and no hepatocellular carcinomas. However, animals initiated with DEN and then given TCDD had a marked increase in enzyme-altered foci. At the higher dose of TCDD, hepatocellular carcinomas were present in five of seven rats. By means of three different enzyme markers used to evaluate the phenotypes of the enzyme-altered foci, a distinct phenotype heterogeneity of the foci was noted with a shift towards phenotypes exhibiting a greater deviation from normal liver when TCDD was given following DEN-partial hepatectomy. Quantitation of the numbers of enzyme-altered foci was performed by relating measurements made from two-dimensional tissue sections to the numbers of foci per unit volume of liver using relationships established in the field of stereology. The total volume of the liver occupied by the enzyme-altered foci, but not their number, increased with the dose of TCDD administered following DEN-partial hepatectomy. These studies demonstrate that TCDD is a potent promoting agent for hepatocarcinogenesis.

Thymidine kinase and deoxyribonucleic acid metabolism in growing and regenerating livers from rats on controlled feeding schedules

Rats accustomed to eating during the first 8h of a daily 12h dark period re-established about 80% of intact liver weight, protein and DNA within 4 days following partial hepatectomy; further increases were not observed. Liver thymidine kinase activity and thymidine incorporation into liver DNA exhibited marked daily oscillations during liver regeneration. Maximum values were observed near the end of the dark period both in intact growing rats and in rats partially hepatectomized 2h before the end of the dark period. The time of day of surgery affected thymidine kinase activity and thymidine incorporation into DNA at specific times following partial hepatectomy. This seriously affects the interpretation of reports of experiments where the time of day of killing has been held constant and time of surgery varied. Highly significant correlation coefficients were observed for thymidine incorporation before killing versus thymidine kinase activity at time of killing and for thymidine versus orotic acid incorporation into DNA of livers from rats partially hepatectomized 2h before the end of the dark period and killed at 12h intervals. Thymidylate phosphatase activity returned to the normal amount at a rate similar to that for liver protein. Thymidylate phosphatase did not affect the validity of the thymidine kinase assay. The relationship of [(14)C]orotic acid to [(3)H]thymidine incorporation into liver DNA varied with the time of day, with the age of the rat and during the regeneration of the liver.

Suppression of murine leukemias by L-asparaginase. Incidence of sensitivity among leukemias of various types: comparative inhibitory activities of guinea pig serum L-asparaginase and Escherichia coli L-asparaginase

A survey of 109 recently derived leukemias of the mouse revealed that sensitivity to suppression by guinea pig serum is a common property of transplanted leukemias of certain classes. The sensitive leukemias included five that arose spontaneously in mice of strains with a low incidence of leukemia and 21 that were induced by X-radiation. Two GPS-sensitive leukemias were not more sensitive than a GPS-resistant leukemia to a range of standard chemotherapeutic agents. The effectiveness of L-asparaginase EC-2 from Escherichia coli in suppression of the GPS-sensitive leukemia EARAD1 depends upon the conditions of assay. Whereas it is not inhibitory when administered as a single dose at the time of inoculation of the leukemia it is considerably more effective than GPS when used in the treatment of established leukemia. Permanent cures of 7-day generalized transplants of EARAD1 can be effected by the administration of 2000 or more units of EC-2. Immunological factors apparently do not contribute to cure as treated survivors are fully susceptible to rechallenge with minimal numbers of cells from the same leukemia. Reinoculated survivors with progressively growing transplants have been successfully retreated with EC-2. The blood clearance of EC-2 L-asparaginase injected into mice is much more rapid than that of GPS L-asparaginase. After intraperitoneal inoculation of the EC-1 L-asparaginase, which does not have leukemia-inhibitory activity, only very low levels of enzyme activity could be detected in the serum. The effectiveness of EC-2 from E. coli and its availability from a virtually limitless source will make it possible to extend the study of inhibition of leukemias and other tumors by L-asparaginase to species other than small rodents.