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Health care providers face a considerable challenge when treating chronic pain patients with prescription opioid medications. Although indications exist for the use of these drugs, their addictive nature and street value render them high-risk targets for abuse, misuse, and diversion. All patients receiving opioids should, therefore, be screened for abuse potential before beginning opioid therapy, be required to sign an opioid agreement, and receive close monitoring throughout the course of their treatment. Patients who present with a history of active substance abuse are at higher risk for iatrogenic dependence and necessitate more frequent monitoring. Herein arise several ethical issues, such as the principle of justice, which mediates equitable treatment for all patients. This review discusses the disease underlying substance abuse and clinical manifestations thereof, as well as relevant pathophysiology, ethical issues, and guidelines for the safe treatment with opioids. This review contains 3 tables and 43 references. Key Words: addiction, ethics, opioids, safety, substance abuse

Neuropathic pain permeates a variety of disease processes and remains a consistent challenge for patient treatment at all levels. Diabetes continues to plague a distinct proportion of healthcare in the United States. Without proper preventative measures, these patients are at high risk for acquiring diabetic peripheral neuropathy (DPN). Similarly, rampant alcohol abuse can likely lead to chronic neuropathic sequelae. These issues increase in proportion with an aging population. There are a variety of malnutrition-based disorders, which can manifest into specific neurological issues. Specifically, vitamins B1, B12, and E and copper deficiencies can all lead to neuropathic disorders that become difficult to treat after prolonged periods of nutritional deprivation. Finally, various chemotherapeutic regimens have many known neuropathic complications. These conglomerations of disease manifestation make metabolic neuropathies a complex topic to fully categorize and understand, but certain pearls are vital in a foundational understanding of this topic.

The performance characteristics of a liquid chromatographic (LC) method for the analysis of decoquinate (DEC) in supplements, premixes, and complete animal feeds at medicating and trace levels were collaboratively studied. DEC is extracted from ground feed samples with 1 calcium chloridemethanol solution using mechanical agitation for 90 min. After centrifugation for 5 min and dilution (if necessary), an aliquot of the extract is diluted with water. The diluted extracts are filtered and analyzed by reversed-phase LC with fluorescence detection. Suspect positive trace-level samples are confirmed by using an alternate excitation wavelength. Fourteen test samples of medicated feeds, supplement, and medicated premix, along with 8 test samples for trace-level analysis, were sent to 13 collaborators (one in Canada, 4 in Europe, and 8 in the United States). Test samples were analyzed as blind duplicates. Acceptable results were received from 12 laboratories for the medicated test samples and from 13 laboratories for the trace-level samples. Repeatability relative standard deviation estimates ranged from 1.3 to 5.6. Reproducibility relative standard deviations estimates ranged from 2.8 to 6.1, and HorRat values ranged from 0.22 to 0.74.

A method using immunoaffinity column chromatography (IAC) and liquid chromatography (LC) for determination of zearalenone in cereal grains, animal feed, and feed ingredients was collaboratively studied. The test portion is extracted by shaking with acetonitrilewater (90 + 10, v/v) and sodium chloride. The extract is diluted and applied to an immunoaffinity column, the column is washed with water or phosphatebuffered saline or methanolwater (30 + 70, v/v), and zearalenone is eluted with methanol. The eluate is evaporated, the residue is dissolved in mobile phase and analyzed by reversed-phase LC with fluorescence detection. The presence of zearalenone can be confirmed using an alternate excitation wavelength or diode array detection. Twenty samples were sent to 13 collaborators (8 in Europe, 2 in the United States, one in Japan, one in Uruguay, and one in Canada). Eighteen samples of naturally contaminated corn, barley, wheat, dried distillers grains, swine feed, and dairy feed were analyzed as blind duplicates, along with blank corn and wheat samples. The analyses were done in 2 sample sets with inclusion of a spiked wheat control sample (0.1 mg/kg) in each set. Spiked samples recoveries were 89116, and for the 18 naturally contaminated samples, RSDr values (within-laboratory repeatability) ranged from 6.67 to 12.1, RSDR values (among-laboratory reproducibility) ranged from 12.5 to 19.7, and HorRat values ranged from 0.61 to 0.90.

A liquid chromatographic (LC) method for the analysis of monensin, narasin, and salinomycin in mineral premixes, supplements, and complete animal feeds at medicating and trace levels was collaboratively studied. The method uses methanolwater (90 + 10) extraction with mechanical shaking for 1 h, filtration, and dilution if necessary. Determination of the 3 ionophores is by reversed-phase LC using post-column derivatization with vanillin and detection at 520 nm. Suspect positive trace-level products and medicated feeds containing unexpected ionophores are confirmed by hexane extraction or post-column derivatization with dimethylaminobenzaldehyde (DMAB). Twenty-five test samples of medicated feeds, supplements, and mineral and drug premixes, and 9 test samples for trace-level analysis were sent to 11 collaborators in Bulgaria, Czech Republic, Portugal, France, The Netherlands, United States, and Canada. Acceptable results were received from 10 laboratories. For the medicated complete feeds, supplements, and mineral premixes, RSDr values (within-laboratory repeatability) ranged from 2.5 to 5.2%, RSDR values (among-laboratory reproducibility) ranged from 2.7 to 6.8%, and HorRat values ranged from 0.31 to 1.30. For the drug premixes, the result variability was excessive and HorRat values ranged from 2.27 to 14.1. For the trace-level test samples, all laboratories correctly identified the analytes and did not report any false positives. RSDr values ranged from 1.3 to 9.5%, RSDR values ranged from 5.2 to 13.1%, and HorRat values ranged from 0.4 to 0.97.

1. The hemorrahgic agent is spoiled sweet clover hay (Melilotus alaba) has been isolatd in a pure state, m. p. 288-289°, from experimentally produced spoiled hays as well as form hyas that killed cattle in argicultural practice. 2. This substance has the empirical formula C12H12O6. It is optically inactive. There are two acidic hydroxyls in the molecule. The acidity of the pure substance falls between that of the phenols and the carboxylic acids. A crystalline dimethyl other C12H12O4(OCH2)2 with a melting point fo 168-170° (physiologically inactive) has been prepared by methylation with diazomethane. 3. In the pure state the substance has a low soulubility in the ordinary organic solvents. It is insoluble in acid media. Basic solvenets. and dilute alkali effect solution radily (salt formation). 4. The substance could not be characterized or identified on the basis of its behavior towards the usual identification reagents. Its occurrence in nature has not previosly been reproted. 5. 1.5 mg. of hte crystalline hemorrhagic agent cause approximately the same reduciton in the prothrombin level or activity of the plasma of standardized susceptible reabbits in 40 hours as 50 gm. of the standard spoiled hay sample. 6. Spoiled sweet cover hays produced experimentally from Melilotus alba and those relized in agricultural parctice contain approximately 0.003 per cent of the hemorrhagic agent on the dry substance basis. The over-all yield of the subsance in a fractionation scheme involving sixteen steps approximates 86 per cent of the quantity present.

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.

A well characterized model of multistage carcinogenesis is that of hepatocarcinogenesis in the rat. The histopathology as well as the cell and molecular biology of the stages of initiation, promotion, and progression have been elucidated to varying degrees in this system. Putatively single initiated hepatocytes are identified by their expression of the ubiquitous marker of hepatocarcinogenesis, glutathione-S-transferase pi (GSTP). 0.5-1.0 x 10(6) GSTP-positive "initiated" hepatocytes developed within 14 days after initiation with a subcarcinogenic dose of diethylnitrosamine (DEN). Approximately 1% of these cells develop clonally into altered hepatic foci (AHF) in animals administered promoting agents, such as phenobarbital, chronically for 4-8 mo. Hepatocytes within AHF during the stage of promotion exhibit normal diploid karyotypes but various phenotypes depending on the chemical nature of the promoting agent. Continued administration of the promoting agent results in the infrequent development of hepatocellular carcinomas; however, administration of a complete carcinogen or a progressor agent during the stage of promotion results in substantial numbers of hepatic neoplasms. In order to quantitate the development of the stage of progression more accurately, markers selective for this stage have been sought. Transforming growth factor-alpha (TGF-alpha) appears to be such a marker of progression. About 500 TGF-alpha-positive lesions develop spontaneously following initiation and continued promotion, usually within GSTP-positive AHF, but administration of a single dose of a progressor agent such as ethylnitrosourea may increase this number 3-fold or more. Some agents such as gamma radiation and hydroxyurea, when administered as single or a few closely spaced multiple doses, result in no increased number in TGF-alpha-positive lesions but a markedly enhanced increase in their growth rate. By monitoring gene expression using quantitative stereology, the stages of hepatocarcinogenesis can be analyzed and quantified in sufficient detail so that the animal data can be utilized in biomathematical modeling to develop more accurate models for estimation of human cancer risks.

The experimental three-stage hepatocarcinogenesis protocol of initiation, promotion, and progression, coupled with the analytical technique of stereology, permits quantitative analysis of the carcinogenic process, including the derivation of biologically based risk assessment models. The aberrant expression of the placental isozyme of glutathione S -transferase (PGST) is an efficient marker for initiated, preneoplastic, and neoplastic hepatocytes. Putatively initiated cells and their clonal progeny can be identified, enumerated, and their growth characteristics determined on the basis of their aberrant expression of this protein. A lack of suitable markers has made the identification and quantitation of hepatocytes in the early stage of progression more difficult. One characteristic of cells in the stage of progression is the evolution of relatively autonomous growth. The alteration of growth factor signalling pathways may provide one mechanism for this observation. The expression of transforming growth factor α (TGF α ) is seen in many malignancies. The initiation-promotion-progression protocol has been used to induce progression in the rat liver. The focal expression of TGF α was found to correlate with areas of progression in rats subjected to this protocol. The ability to identify and quantitate cells in the stage of progression should facilitate application of the Moolgavkar-VenzonKnudson model for assessing human risk from carcinogens active at each of these three stages. Validation of this model will require determination of the number and growth characteristics of hepatocytes in the stage of progression.

A normal-phase high-performance liquid chromatographic procedure is presented for the determination of robenidine following derivatization with dansyl chloride. The derivatization, separation and detection conditions were optimized. The dansyl derivative is first purified on a silica gel cartridge followed by HPLC analysis on a silica gel column. The eluate is monitored by fluorescence detection at 320 nm excitation and 485 nm emission wavelength. The lower limit of detection of robenidine is 0.4 μg/ml.

A method for melengestrol acetate (MGA) was developed to accurately determine 0.08-220 ppm MGA in animal feeds. MGA is extracted from an aqueous slurry of feed sample with hexane and partitioned from hexane into aqueous methanol and then into dichloromethane. After evaporation of the dichloromethane, the dried extract is transferred with chloroform into a volumetric flask. An aliquot is pipetted into a mixed column of silica gel and acid aluminum oxide, and the MGA is eluted with hexane-acetone. The residue is dissolved in methanol, and the MGA is quantitated by reversed-phase liquid chromatography (LC). The method was validated by using commercial feeds and laboratory-fortified feeds. The method was also applied successfully to corn silages supplemented with MGA. Recoveries [and associated coefficients of variation (CVs)] for feeds fortified in the laboratory with MGA 100 at 0.2,0.8, and 5 ppm were 96.9 (6.28), 102 (3.59), and 109% (2.06%), respectively. CVs for a variety of commercial feeds varied from 0.88 to 3.84%. An inter laboratory study was also conducted to compare the LC method to the AOAC gas chromatographic method.

Fluoride flux in the rabbit CCD: A pH-dependent event. We measured fluoride flux (JF; pmol · min-1 · mm-1) in the isolated rabbit cortical collecting duct (CCD) to investigate the determining factors of JF. The perfusate contained 100 µM fluoride and the bath was fluoride-free. Osmotically-induced lumen-to-bath water flux did not affect JF. When perfusate pH was reduced from 7.4 to 6.1 and from 6.1 to 5.0, JF increased from 0.008 ± 0.002 to 0.027 ± 0.007 (P < 0.01) and from 0.018 ± 0.003 to 0.040 ± 0.005 (P < 0.01), respectively. Acetazolamide at 10-4M in the bath reduced JF slightly though not statistically. The anion-transport inhibitor, 4,4′-diisothiocyanato-stilbene-2,2′-disulfonic acid (DIDS), at 10-4M in the perfusate did not affect JF. Substitution of luminal chloride with gluconate failed to affect JF in tubules from normal rabbits or from rabbits treated with deoxycorticosterone which stimulates chloride-bicarbonate exchange in the CCD. JF showed no correlation with transepithelial voltage which ranged from +4 to -104 mV. We conclude that the luminal pH represents the primary determining factor influencing JF in the rabbit CCD, and fluoride does not use a chloride-mediated or a DIDS-inhibitory transport pathway.

The performance characteristics of a liquid chromatographic (LC) method for the analysis of decoquinate (DEC) in supplements, premixes, and complete animal feeds at medicating and trace levels were collaboratively studied. DEC is extracted from ground feed samples with 1% calcium chloride-methanol solution using mechanical agitation for 90 min. After centrifugation for 5 min and dilution (if necessary), an aliquot of the extract is diluted with water. The diluted extracts are filtered and analyzed by reversed-phase LC with fluorescence detection. Suspect positive trace-level samples are confirmed by using an alternate excitation wavelength. Fourteen test samples of medicated feeds, supplement, and medicated premix, along with 8 test samples for trace-level analysis, were sent to 13 collaborators (one in Canada, 4 in Europe, and 8 in the United States). Test samples were analyzed as blind duplicates. Acceptable results were received from 12 laboratories for the medicated test samples and from 13 laboratories for the trace-level samples. Repeatability relative standard deviation estimates ranged from 1.3 to 5.6%. Reproducibility relative standard deviations estimates ranged from 2.8 to 6.1%, and HorRat values ranged from 0.22 to 0.74.

A method using immunoaffinity column chromatography (IAC) and liquid chromatography (LC) for determination of zearalenone in cereal grains, animal feed, and feed ingredients was collaboratively studied. The test portion is extracted by shaking with acetonitrile-water (90 + 10, v/v) and sodium chloride. The extract is diluted and applied to an immunoaffinity column, the column is washed with water or phosphate-buffered saline or methanol-water (30 + 70, v/v), and zearalenone is eluted with methanol. The eluate is evaporated, the residue is dissolved in mobile phase and analyzed by reversed-phase LC with fluorescence detection. The presence of zearalenone can be confirmed using an alternate excitation wavelength or diode array detection. Twenty samples were sent to 13 collaborators (8 in Europe, 2 in the United States, one in Japan, one in Uruguay, and one in Canada). Eighteen samples of naturally contaminated corn, barley, wheat, dried distillers grains, swine feed, and dairy feed were analyzed as blind duplicates, along with blank corn and wheat samples. The analyses were done in 2 sample sets with inclusion of a spiked wheat control sample (0.1 mg/kg) in each set. Spiked samples recoveries were 89-116%, and for the 18 naturally contaminated samples, RSDr values (within-laboratory repeatability) ranged from 6.67 to 12.1%, RSDR values (among-laboratory reproducibility) ranged from 12.5 to 19.7%, and HorRat values ranged from 0.61 to 0.90.

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.

A liquid chromatographic method for determining residues of ionophores in bovine, porcine, and avian tissues is described. Tissues were extracted with iso‐octane‐ethyl acetate and the extracts purified on silica solid‐phase extraction columns. Monensin, narasin and salinomycin were detected by UV absorbance following post‐column derivatization with vanillin, and lasalocid was detected underivatized using fluorescence. In muscle, kidney and fat, all drugs were determined from a single sample extract. In liver, a separate extraction was done to determine lasalocid. The detection limit for lasalocid, narasin and salinomycin was 5 ppb; for monensin it was 2ppb. Average recoveries were: lasalocid—71.0%; monensin—94.3%; salinomycin—97.2%; narasin—94.1 %.

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.

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.

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), γ-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.

Although biological processes are, in general, far more complex than chemical and physical phenomena, one goal of biology, toxicology, and pathology is the mathematical-statistical formulation of models that describe the mechanisms of normal and disease processes. However, as pointed out by several scientists (Whittemore, 1978; Moolgavkar, 1986; Alavanja et al., 1987), up to this time no mathematical-statistical model of a biological process has faithfully described all of the particulars of the biological phenomenon under consideration. This is especially true in the field of carcinogenesis (cf. Chu, 1987) where many models have been proposed in the past. With any model, however, its formulation is dependent on the level of knowledge of the biological mechanisms controlling the process, i.e., carcinogenesis. Recent advances in our understanding of the mechanisms of carcinogenesis as a multistage process have allowed, at least potentially, for a closer congruence between models representative of carcinogenesis and their pathogenesis.

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.

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.

Summary This article has described the minimum laboratory and mouth procedures needed for fabrication of the Thompson dowel-rest removable partial denture using the modifications of (1) preconstructructed dies for the dowel-rests, (2) a chrome-cobalt framework, and (3) a ball clasp retention device.

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.

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.

1. The hemorrahgic agent is spoiled sweet clover hay (Melilotus alaba) has been isolatd in a pure state, m. p. 288-289°, from experimentally produced spoiled hays as well as form hyas that killed cattle in argicultural practice. 2. This substance has the empirical formula C12H12O6. It is optically inactive. There are two acidic hydroxyls in the molecule. The acidity of the pure substance falls between that of the phenols and the carboxylic acids. A crystalline dimethyl other C12H12O4(OCH2)2 with a melting point fo 168-170° (physiologically inactive) has been prepared by methylation with diazomethane. 3. In the pure state the substance has a low soulubility in the ordinary organic solvents. It is insoluble in acid media. Basic solvenets. and dilute alkali effect solution radily (salt formation). 4. The substance could not be characterized or identified on the basis of its behavior towards the usual identification reagents. Its occurrence in nature has not previosly been reproted. 5. 1.5 mg. of hte crystalline hemorrhagic agent cause approximately the same reduciton in the prothrombin level or activity of the plasma of standardized susceptible reabbits in 40 hours as 50 gm. of the standard spoiled hay sample. 6. Spoiled sweet cover hays produced experimentally from Melilotus alba and those relized in agricultural parctice contain approximately 0.003 per cent of the hemorrhagic agent on the dry substance basis. The over-all yield of the subsance in a fractionation scheme involving sixteen steps approximates 86 per cent of the quantity present.

Summary and ConclusionsIn man as in the rat, salicylate in adequate dosage induces prothrombinopenia which can be prevented by vitamin K compounds, if liver function is adequate. The effect on the prothrombin level (or activity) is detected most readily by the use of 12.5% plasma. The dietary intake particularly of vitamin K appears to play a significant role in determining the extent and duration of the prothrombinopenia. Cirrhosis of the liver and pre-existing prothrombinopenia augment the effect of salicylate. Acetyl salicylic acid appears to be a more potent agent than sodium salicylate. The action of salicylate is apparently identical with that of the anticoagulant dicumarol, but less effective. The two drugs can complement each other. This may be useful in the clinical application of dicumarol and should be realized to avoid excess prothrombinopenia.

“Quorum pars magna fui.” These words Superintendent Campbell could use with propriety in speaking of vocational guidance in New York City schools, for he has been active in that movement ever since he became an associate superintendent. Guidance has been especially fostered by the development of the continuation schools, which have matured into vocational high schools. While many places have curtailed, and some places have eliminated, guidance activities, New York, although compelled to retrench wherever possible, has expanded those activities. This circumstance is the best possible proof of the truth of Dr. Campbell's statement that New York schools are “guidance conscious.” In view of his record, it is not surprising, but it is highly gratifying none the less, that the Superintendent of Schools of the largest city in the land should pledge himself, as Dr. Campbell does at the end of this article, to continued support of sound vocational guidance.

SummaryThe difference between prothrombin times of whole and diluted plasma is a more reliable guide to prothrombin activity of the blood than is the prothrombin time of either alone. The difference has been found to be fairly constant in normal individuals. When prolonged, it indicates hypoprothrombinemia. When reduced, it may signify hyperprothrombinemia or an excess of anticoagulants in the blood. The procedure recommended is well suited for following the therapeutic effects of agents which influence the prothrombin level (or activity) such as dicumarol or vitamin K.

Lamenting the uncertainty that jurists sometimes have of the ultimate wisdom of their decisions, Judge Cardozo once remarked upon the peace of mind that must come to the designer of a mighty bridge