Transiently increased glutamate cycling in rat PFC is associated with rapid onset of antidepressant-like effects.

Several drugs have recently been reported to induce rapid antidepressant effects in clinical trials and rodent models. Although the cellular mechanisms involved remain unclear, reports suggest that increased glutamate transmission contributes to these effects. Here, we demonstrate that the antidepressant-like efficacy of three unique drugs, with reported rapid onset antidepressant properties, is coupled with a rapid transient rise in glutamate cycling in the medial prefronal cortex (mPFC) of awake rats as measured by ex vivo 1H-[13C]-nuclear magnetic resonance spectroscopy. Rats were acutely pretreated by intraperitoneal injection with a single dose of ketamine (1, 3, 10, 30 and 80 mg kg-1), Ro 25-6981 (1, 3 and 10 mg kg-1), scopolamine (5, 25 and 100 µg kg-1) or vehicle (controls). At fixed times after drug injection, animals received an intravenous infusion of [1,6-13C2]glucose for 8 min to enrich the amino-acid pools of the brain with 13C, followed by rapid euthanasia. The mPFC was dissected, extracted with ethanol and metabolite 13C enrichments were measured. We found a clear dose-dependent effect of ketamine and Ro 25-6981 on behavior and the percentage of 13C enrichment of glutamate, glutamine and GABA (γ-aminobutyric acid). Further, we also found an effect of scopolamine on both cycling and behavior. These studies demonstrate that three pharmacologically distinct classes of drugs, clinically related through their reported rapid antidepressant actions, share the common ability to rapidly stimulate glutamate cycling at doses pertinent for their antidepressant-like efficacy. We conclude that increased cycling precedes the antidepressant action at behaviorally effective doses and suggest that the rapid change in cycling could be used to predict efficacy of novel agents or identify doses with antidepressant activity.

Effects of ANK3 variation on gray and white matter in bipolar disorder.

The single-nucleotide polymorphism rs9804190 in the Ankyrin G (ANK3) gene has been reported in genome-wide association studies to be associated with bipolar disorder (BD). However, the neural system effects of rs9804190 in BD are not known. We investigated associations between rs9804190 and gray and white matter (GM and WM, respectively) structure within a frontotemporal neural system implicated in BD. A total of 187 adolescent and adult European Americans were studied: a group homozygous for the C allele (52 individuals with BD and 56 controls) and a T-carrier group, carrying the high-risk T allele (38 BD and 41 controls). Subjects participated in high-resolution structural magnetic resonance imaging and diffusion tensor imaging (DTI) scanning. Frontotemporal region of interest (ROI) and whole-brain exploratory analyses were conducted. DTI ROI-based analysis revealed a significant diagnosis by genotype interaction within the uncinate fasciculus (P⩽0.05), with BD subjects carrying the T (risk) allele showing decreased fractional anisotropy compared with other subgroups, independent of age. Genotype effects were not observed in frontotemporal GM volume. These findings support effects of rs9804190 on frontotemporal WM in adolescents and adults with BD and suggest a mechanism contributing to WM pathology in BD.

Abstinence-related changes in sleep during treatment for cocaine dependence.

BACKGROUND: Former sleep studies among non-treatment seeking chronic cocaine users had captured polysomnographic changes for as long as three weeks of abstinence. METHODS: 20 cocaine dependent participants, randomized to placebo in an ongoing clinical trial, received 12 days of inpatient substance abuse treatment followed by 6 weeks of outpatient cognitive behavioral therapy. Polysomnographic recording was performed on consecutive nights during the 1st and 2nd inpatient and 3rd and 6th outpatient weeks. Number of days abstinent was determined from thrice weekly urine toxicology and self-report. Polysomnographic sleep was compared between study week 1 and 2, using paired t-tests. Trajectory of total sleep time (TST) was modeled both as a linear and a quadratic function of days abstinent. RESULTS: Despite reporting an improvement in overall sleep quality, polysomnographic sleep worsened from week 1 to 2. Among all participants, TST and stage 2 sleep time decreased, while REM sleep latency increased. Among participants who began the study with a positive urine test, there was also a decrease in REM and a trend for decreased slow wave sleep. TST compared to number of days abstinent (up to 54 days) was best fit with a quadratic model (p=0.002), suggesting the possibility of an improvement in total sleep time with extended abstinence. CONCLUSIONS: This is the first polysomnographic characterization of sleep in a large sample of cocaine users in treatment. Present findings confirm earlier results of poor and deteriorating sleep early in abstinence, and raise the possibility of improvement after an extended abstinence.

A single-day paradigm of self-regulated human cocaine administration.

UNLABELLED: Prior work by our group has shown the feasibility, safety, and validity of a multi-day, multi-dose paradigm of self-regulated cocaine administration in humans. The current work sought to consolidate these methods in a single-day design focused on reducing logistical complexity, decreasing research burden to human subjects, and increasing suitability for medication development designs. METHODS: Eleven experienced cocaine users participated in a 6-hour, single-day design, consisting of one safety/eligibility and three experimental cocaine periods (during which subjects were allowed to self-administer 8, 16, and 32 mg/70 kg cocaine doses under a fixed-ratio 1:5 minute timeout schedule). Changes in cocaine-induced cardiovascular response, self-administration behavior, and subjective effects were assessed. RESULTS: Procedures were well tolerated by participants, and no significant adverse events were noted. Significant (p < 0.05), changes in measures of cocaine self-administration (e.g., responses, infusions, interinfusion intervals, consumption, and plasma levels), cardiovascular response (HR), and subjective effects ("high") were observed. In contrast, cocaine-induced increases in other vital signs (e.g., SBP, DBP) and subjective effect measures (e.g., paranoia) did not differ between doses. CONCLUSIONS: These data support the safety, tolerability and validity of our single-day design. Depending on the application, such methods may afford advantages for assessing the self-regulation of cocaine administration behavior in humans (e.g., including medication development designs).

A multistudy analysis of the effects of early cocaine abstinence on sleep.

OBJECTIVE: To describe the sleep patterns of early cocaine abstinence in chronic users by polysomnographic and subjective measures. METHODS: 28 cocaine-dependent participants (ages 24-55) underwent polysomnographic sleep (PSG) recording on the 1st, 2nd and 3rd weeks of abstinence on a research dedicated inpatient facility. Objective measures of total sleep time, total REM time, slow wave sleep, sleep efficiency and a subjective measure (sleep quality) along with demographic data were collected from three different long term research studies over a five year period. Data were reanalysed to allow greater statistical power for comparisons. RESULTS: Progressive weeks of abstinence had main effects on all assessed PSG sleep measures showing decreased total sleep time, REM sleep, stages 1 and 2 sleep, and sleep efficiency; increases in sleep onset and REM latencies and a slight increase in slow-wave sleep time were also present. Total sleep time and slow wave sleep were negatively associated with years of cocaine use. Total sleep time was positively associated with the amount of current ethanol use. Sex differences were found with females having more total REM time and an increase at a near significance level in slow wave sleep. Subjective measures were reported as improving with increasing abstinence over the same time period. CONCLUSIONS: Chronic cocaine users show a general deterioration in objective sleep measures over a three-week period despite an increase in subjective overall sleep quality providing further evidence for "occult insomnia" during early cocaine abstinence.

Ethanol-like effects of thiopental and ketamine in healthy humans.

The gamma-aminobutyric acid-A (GABA(A)) and N-methyl-D-aspartate (NMDA) receptors mediate aspects of the behavioural effects of alcohol. Prior studies reported drugs that block NMDA receptors or facilitate GABA(A) receptor function produce ethanol-like effects in humans. The purpose of this study was to compare the ethanol-related effects of two pharmacological agents with known NMDA and GABA(A) receptor activity. As part of an ongoing, larger study, 28 subjects (age, 21-30) with no personal or family histories of alcoholism were administered subanesthetic doses of the GABA(A) receptor agonist thiopental, the NMDA receptor antagonist, ketamine and placebo on three separate test days. Various ethanol-related measures were administered. At doses of thiopental and ketamine that produced similar levels of sedation and cognitive effects, both agents produced significant ethanol-like effects and subjective intoxication. However, the intensity of the ethanol-like effects of ketamine was greater than that of thiopental. In addition, ketamine produced alterations in perception that were not produced by thiopental. These data provide further support for a model where GABA(A) receptor facilitation may contribute significantly to ethanol effects associated with social drinking, whereas NMDA receptor antagonism may contribute to relatively greater extent to features of ethanol 'intoxication'.

A paradigm to investigate the regulation of cocaine self-administration in human cocaine users: a randomized trial.

RATIONALE: We recently conducted a pilot study supporting the feasibility, safety, and validity of a human laboratory model of ad libitum cocaine administration in which subjects self-selected the timing of infusions. The current study extends this work to include a randomized design with a test-retest component in a larger sample. OBJECTIVES: To investigate the regulation of cocaine intake by humans and its effects on subjective and cardiovascular responses. MATERIALS AND METHODS: Subjects were 14 non-treatment seeking volunteers (10 M, 4 F) with cocaine abuse/dependence. Subjects self-administered cocaine infusions (0, 8, 16, and 32 mg/70 kg) over a 2-h period under a fixed ratio 1, 5-min time-out schedule on 4 consecutive days. A fifth session was conducted at 16-mg dose to assess the paradigm's test-retest reliability. RESULTS: Subjects regulated their cocaine intake in a dose-dependent fashion. Self-reports of cocaine-related subjective effects (e.g., "high" and "stimulated") also varied in a dose-dependent way. Test-retest data and the randomized design support the conclusion that such effects are not due to tolerance or other experimental artifacts. CONCLUSION: The current study replicates prior work demonstrating the feasibility, safety, and validity of our human laboratory paradigm of cocaine administration in a larger sample using a randomized design. The current study also shows the test-retest reliability of these methods, establishing its utility for comparisons of experimental interventions (e.g., pharmacological treatments). Finally, the current study suggests that factors other than drug-induced euphoria (i.e., "high") contribute to the regulation of cocaine-taking behaviors in humans.

Gynecologic cancer patients' psychosocial needs and their views on the physician's role in meeting those needs.

The aim of this study was to identify the psychosocial needs of patients after treatment for gynecological malignancies and their views concerning the role physicians should take in meeting those needs. Self-administered questionnaires were answered by 95 patients at least 6 months after completion of therapy. Topic areas included emotional needs, spiritual concerns, patient-family communication, patient participation in decision making, and advance directives. In addition, all participants completed the Functional Assessment of Cancer Therapy (FACT-G, version 4) quality of life questionnaire. Fifty-seven percent of respondents stated that they had needed help dealing with emotional problems, and 73% wanted the physician to ask whether help is needed. The most common emotional concerns were feeling nervous (40% of subjects), being worried (34%), fear (25%), needing someone to talk to (24%), sadness (21%), and loss of control (17%). Fifty-nine percent stated that physicians should ask whether help is needed in discussing spiritual matters. Sixty-one percent stated that physicians should ask patients whether they want help starting conversations with their families about difficult-to-raise topics such as the possibility of dying. Forty-six of 86 respondents (53%) stated that discussions about advance directives such as living wills should take place soon after the cancer diagnosis has been established. Most patients surveyed want physicians to take an active role in dealing with psychosocial needs.

Effect of soy protein isolate and conjugated linoleic acid on the growth of Dunning R-3327-AT-1 rat prostate tumors.

BACKGROUND: Epidemiologic and animal model studies suggest that consumption of soy isoflavones may be associated with reduced risk of prostate cancer (PC). In addition, animal model studies suggest that conjugated linoleic acid (CLA), a natural positional isomer of linoleic acid, inhibits tumor growth in various models, including models of PC. METHODS: Based on the above-mentioned data, the objective of the present study was to test the hypothesis that supplementation of the diet with combinations of isoflavone-rich soy protein isolate and CLA would act to inhibit the growth of androgen-independent R-3327-AT-1 rat prostate tumor cells inoculated ectopically into male Copenhagen rats. RESULTS: The results of this study indicate that neither an isoflavone-rich soy protein isolate (SPI), nor CLA inhibit the in vivo growth and development of prostate tumor cells when administered in the diet either singly or in combination. Moreover, at the highest concentrations SPI and CLA (i.e., 20% SPI, 1% CLA), there was a statistically significant increase in tumors volume over controls. Administration of SPI at 10% in the diet also enhanced tumor growth, whereas at 5%, SPI exerted no measurable effect. CLA administration alone had no observable effects on AT-1 tumor growth. CONCLUSION: These results, in an established rat model, suggest caution in using isoflavone-rich SPI in human studies involving advanced hormone-refractory prostate cancer until further investigation of these effects are completed.

LAS, a novel selective estrogen receptor modulator with chemopreventive and therapeutic activity in the N-nitroso-N-methylurea-induced rat mammary tumor model.

The N-nitroso-N-methylurea-induced rat mammary tumor model was used to conduct two types of studies: a prevention study designed to test the ability of the novel selective estrogen receptor modulator lasofoxifene (LAS) to inhibit the development of mammary tumors, and a treatment study designed to test the inhibitory effect of LAS on the growth of established tumors. The prevention study indicated that LAS markedly delayed the emergence of N-nitroso-N-methylurea-induced tumors to an extent similar to that obtained by the established antiestrogen tamoxifen (TAM). At the highest dose administered, both TAM and LAS reduced tumor incidence by 75% and total tumor number by 90% relative to the controls. LAS also reduced the multiplicity of tumors, i.e., the mean number of tumors per rat, and resulted in substantially smaller total tumor burden. In the treatment study, LAS significantly inhibited tumor growth compared with the controls. In addition, whereas none of the untreated tumors regressed completely over the experimental period, 40% of LAS-treated tumors regressed by >50% at the highest dose (10 mg/kg daily). The results of this study in a rat mammary tumor model indicate that LAS has both chemopreventive and chemotherapeutic effects quantitatively comparable with those of TAM.

Feeding thiol-containing compounds, derived from vegetables, fails to inhibit N-methylnitrosourea-induced mammary tumorigenesis.

Various thiol-containing compounds have been shown to inhibit chemically-induced tumors in animal models. Two thiol-containing compounds derived from vegetables, namely 1,2 dithiol-3-thione (DTT) and S-methylmethane thiolsulfonate (MMTS), were tested for their chemopreventive activity in the N-methylnitrosourea (NMU)-induced rat mammary tumor model. Each compound was incorporated into the grain-based Teklad 7001 diet and fed to the rats one week prior to initiation with NMU until termination 18 weeks post NMU. DTT was fed at 166 and 500 ppm and MMTS at 200 and 800 ppm. Neither compound exerted a significant inhibitory effect on any index of tumor development including incidence, total tumor, tumor multiplicity, volume or latency. Serum levels of DTT assessed at termination in the 500 ppm DTT group ranged from 10-30 microg/ml. MMTS was undetectable in serum from either MMTS-fed group. The results of this study, using the direct acting carcinogen, NMU, suggest that the chemopreventive effect of thiol-containing compounds may be confined to animal models using carcinogens that require host activation.

Investigation of commercial Mitolife as an antioxidant and antimutagen.

Coronary heart disease and many types of cancer are important diseases in the world and especially in Western countries. There are biochemical activation processes for low-density lipoprotein cholesterol and genotoxic carcinogens to reactive products. In part, these also involve the generation of active oxygen and reactive oxygen species. We investigated the effect of a natural product, MitoLife, which contains a mixture of fruit and tea extracts, on the oxidation of low-density lipoprotein cholesterol and the mutagenicity of five genotoxic carcinogens, specifically, 2-acetylaminofluorene, 2-aminoanthracene, 2-amino-3-methylimidazo[4,5-f]quinoline, aflatoxin B(1), and benzo[a]pyrene. A positive antioxidant control, polyphenon 60, a concentrate of green-tea polyphenols, was used to compare the effect of MitoLife with that of polyphenon. MitoLife displayed inhibiting effects in all series of tests at slightly lower effectiveness but with the same order of magnitude as the green-tea polyphenol product. Thus, MitoLife represents another means to decrease adverse effects associated with the oxidation of low-density lipoprotein cholesterol or of a series of carcinogens, some of which are in the human environment.

The influence of different varieties of olive oil on N-methylnitrosourea(NMU)-induced mammary tumorigenesis.

Several epidemiological and animal model studies suggest that consumption of olive oil, which is rich in the monounsaturated fatty acid, oleic acid (OA, C18:, n-9) may reduce the risk of breast cancer. There are however, a wide variety of olive oils in the marketplace with levels of OA ranging from a low of 50% to a high of 80% OA. The purpose of this rodent model study was to determine whether the level of OA in olive oil is a key determinant of its protective effects. We compared the inhibitory effects among three different types of olive oil containing 54, 70 and 80% OA and 20, 15 and 5% linoleic acid (LA), respectively, corn oil and a store bought olive oil, using the NMU-induced rat mammary tumor model. While little difference was found in total mammary tumor yields, a differential effect was found in the histological type of tumors formed. Olive oil containing 80% OA and 5% LA exhibited the lowest level of adenocarcinomas and the highest level of the more benign adenocarcinoma arising from within a fibroadenoma. While the reasons for this effect remain to be clarified, these results suggest that future studies on the health benefits of olive oil should take into account the type as well as the amount of olive oil.

Effect of intact and isoflavone-depleted soy protein on NMU-induced rat mammary tumorigenesis.

Experiments in animal models of carcinogenesis suggest that soy consumption decreases tumor number and incidence. Genistein, an isoflavone which is present in soy at high concentrations, has been considered to be the primary antitumor constituent in soy. In the present study, the N-nitroso-N-methylurea (NMU)-induced mammary tumor model was used as a means to determine whether the chemopreventive effect of soy was attributable specifically to its high content of isoflavones. Five groups of rats (30/group) were fed the following modified AIN-93G diets: group 1, 20% intact soy protein (SP); group 2, 10% SP; group 3, 20% isoflavone-depleted soy protein (IDSP); group 4, 10% IDSP; group 5, the casein-based AIN-93G diet. The SP contained 1.07 and IDSP 0.073 mg genistein/g isolate, respectively. Experimental diets were initiated 1 week prior to NMU administration (at 50 days of age) and continued for another 18 weeks. No significant differences were found among the five groups when assessed in terms of tumor incidence, latency, multiplicity or volume. A trend towards inhibition was observed in both the 20 and 10% SP and IDSP groups when assessed in terms of total tumors/group, tumor volume and latency, but this trend did not achieve statistical significance. The results of this model study do not support the hypothesis that the isoflavone components of soy protein, or soy protein itself, inhibit chemically induced mammary tumor development.

Effect of dietary lycopene on N-methylnitrosourea-induced mammary tumorigenesis.

Epidemiological studies suggest protective effects of lycopene-rich foods on several types of cancer, including prostate and gastrointestinal tract. Moreover, an inverse association between serum lycopene concentrations and several types of cancer has been reported. However, few studies have focused on breast cancer, and they have shown little association between lycopene consumption and cancer risk. In this report, we used the N-methylnitrosourea (NMU)-induced rat mammary tumor model to compare the effects of pure lycopene with a lycopene-rich tomato carotenoid oleoresin (TCO) on NMU-induced mammary tumorigenesis. Rats were fed diets supplemented with 250 and 500 ppm crystalline lycopene or TCO beginning seven days before initiation with NMU (55 days of age) to termination (18 wk after NMU). Neither pure lycopene nor lycopene in the form of a mixed carotenoid oleoresin exerted an inhibitory effect on tumor incidence, latency, multiplicity, volume, or total tumors per group compared with unsupplemented controls. Weight gains in all groups were similar. Assay of serum lycopene concentrations in lycopene-supplemented groups indicated that median levels of 7,12,60, and 87 ng/ml were attained in blood of groups supplemented with 250 and 500 ppm lycopene and 250 and 500 ppm TCO, respectively. The results of this animal study are consistent with epidemiological reports indicating that lycopene does not protect against breast cancer.

Diethylnitrosamine exposure-responses for DNA ethylation, hepatocellular proliferation, and initiation of carcinogenesis in rat liver display non-linearities and thresholds.

In previous exposure-response studies, we have documented non-linearities for some of the early effects in rat liver of diethylnitrosamine (DEN) and a near no-effect levels for initiation of promotable liver neoplasms at the lowest cumulative exposure of 0. 5 mmol/kg body weight; this in spite of formation of DNA adducts and induction of hepatocellular altered foci (HAF). To extend these investigations, in an initiation segment, young male F344 rats were administered four exposures of DEN ranging from a cumulative total of 0.25 mmol, which is half of the previously used low exposure, up to 2 mmol per kg body weight, an effective initiating exposure. These exposures were achieved by once weekly intragastric instillations of one-tenth the total exposures for up to 10 weeks. The initiation segment was followed by a 4 week recovery segment, to allow for remission of acute and subchronic effects of DEN, after which the groups were maintained on 0.06% phenobarbital in the diet for 24 weeks to promote liver tumor development in order to assess initiation. During and after initiation and at the end of recovery, selected groups were studied for several crucial effects involved in hepatocarcinogenicity. The low exposure produced a low-level of DNA ethylation at both 5 and 10 weeks of exposure, measured as O(4)-ethylthymidine, the most persistent promutagenic ethylation product. At the 5 week interval, the adduct values of the higher exposures were less than proportional to the increment of exposure, suggestive of nonlinearity. Assessment of cellular proliferation by staining for proliferating cell nuclear antigen revealed that the lowest exposure did not increase the replicating fraction of hepatocytes during the initiation (10 weeks) or recovery (4 weeks) segments, whereas in the three higher exposure groups, proliferation was increased in relation to dose and time. Preneoplastic HAF expressing glutathione S-transferase-placental-type were present at low multiplicity in control livers and their multiplicity was increased in all exposure groups by the end of exposure, at which time the increase in the high exposure group was disproportionately greater than the increment of exposure. After phenobarbital administration in the promotion segment, all exposure groups exhibited further HAF increases at 39 weeks. At the end of the promotion segment, no hepatocellular neoplasm was found in 80 controls or in 40 rats in the low exposure group. In the mid-low exposure group, which was the previously studied low exposure, only one adenoma was found, yielding a 3% incidence, while in the two higher exposure groups, 32 and 80% of rats exhibited liver neoplasms, which were increased disproportionately greater than the increments of exposure. Thus, the findings document non-linearities of early DEN effects and at the lowest cumulative dose, a no-effect level (NEL) or threshold for initiation of promotable liver neoplasms. These findings provide a conceptual basis for understanding why low-level exposures to DNA-reactive carcinogens may convey no cancer risk.

Nutrient intake of Head Start children: home vs. school.

OBJECTIVE: To determine mean intake of energy and protein, total fat, saturated fat, percent energy from total and saturated fat, cholesterol, carbohydrate, calcium, iron, zinc, folate, vitamins A, C, E, B-6 and B-12, thiamin, niacin, riboflavin, magnesium, sodium and fiber of preschool Head Start children at school and away from school. DESIGN: Twenty-four-hour food intakes for 358 Head Start children were obtained by observing food intake at school and acquiring intake recalls from parents or guardians specifying food their children consumed for the balance of the day. After determining group estimates of energy and nutrient intake, mean intake was compared to standard nutrient recommendations for the entire 24-hour day, i.e., for the time the children were in school and for the remaining hours away from school ("home" intake). SUBJECTS: The 358 Head Start children attended school either half-day (2- to 3-hour AM and PM sessions) or all-day (5 to 6 hours). STATISTICAL ANALYSES: Differences in nutrient intake among class times were analyzed using one-way analysis of variance (ANOVA) followed by Tukey's multiple comparison test. Differences with a p-value <0.05 (two-tailed) were considered to be statistically significant. Total energy, protein, calcium, iron, zinc, vitamins A, C, E, B6, and B12, thiamin, niacin, riboflavin as well as folate and magnesium were compared to the Recommended Dietary Allowances for the 4- to 6-year-old age group. Other standards that were used for comparisons included the National Cholesterol Education Program (fat, saturated fat and cholesterol), the 1989 National Research Council's Diet and Health Report (carbohydrate and sodium) and the recommendation for fiber proposed by the American Health Foundation. RESULTS: At school, half-day children consumed up to 25% of the daily recommendation for energy and nutrients, while all-day children achieved at least a third of the recommended intakes. When intakes at home and school were combined, all three groups of children (AM, PM and all-day) exceeded dietary recommendations for protein, vitamins and minerals. Energy intake remained below 100% of the recommendation, while intake of total fat, saturated fat and cholesterol exceeded recommendations. APPLICATION: Further research is required to explore energy needs and determine nutritional status and nutrient needs of minority and low-income preschool children. Strategies are required to increase nutrient density, but not fat density, of meals and snacks served to children who attend day care for part of the day. Finally, school meals and nutrition education programs such as Team Nutrition should broaden their base to include healthful eating habits for all school children, including the very youngest children in preschool programs.

Oral enzyme therapy and experimental rat mammary tumor metastasis.

Although there has been much interest over the years in the medical use of orally administered proteolytic enzymes, there is considerable controversy about their efficacy against advanced stages of cancer. In light of this, the goal of the present study was to assess the inhibitory effects of different doses of an orally administered porcine pancreas preparation on the growth and metastasis of the R13762 transplantable rat mammary tumor. Five groups of 12 F-344 female retired breeders were inoculated orthotopically with a 2mm3 tumor implant and placed on the following diets: (1) AIN-76A diet + 20% porcine pancreas preparation (PPP); (2) AIN-76A + 20% PPP + 10 mg Mg citrate/rat/day; (3) AIN-76A + 2% PPP; (4) AIN-76A + 2% PPP + 10 mg Mg citrate and (5) AIN-76A only (control). Primary tumor development was monitored for 40 days and following sacrifice, lungs were excised, stained and metastatic foci quantitated. Metastatic foci were sorted into 3 groups based on their radii: small (<1mm), medium (1-3mm) and large (>3mm), and volumes calculated. The oral enzyme preparation had no effect on primary tumor growth or on body weight change over the duration of the study. The percent (incidence) of rats with pulmonary metastases among the five groups were not significantly different. However, among the three size categories of pulmonary foci, decreased incidence was found only in the large (>3mm) volume subset of the 2% PPP group supplemented with Mg++. When assessed in terms of mean number of pulmonary foci/rat, the 20% PPP group exhibited the highest and controls the lowest frequency with the important exception of the 2% PPP + Mg++ group (large volume) which exhibited the lowest frequency of all treatment groups. In general, the presence of Mg++ resulted in marked decreases in mean number of pulmonary foci/rat compared to groups fed PPP without the Mg++ supplement. Similar results were obtained when foci were quantitated in terms of metastatic volume rather than frequency. The results of this laboratory animal study suggest that to show effective inhibition of metastatic dissemination of the R13762 tumor by PPP, lower doses of PPP and larger numbers of animals, to account for the high variability in the model, will be required.

S-allylcysteine, a garlic constituent, fails to inhibit N-methylnitrosourea-induced rat mammary tumorigenesis.

Epidemiological and experimental studies suggest that consumption of garlic may protect against several types of cancer. Moreover, a plausible hypothesis has been proposed that the biological effects of garlic can be attributed to the enhancing action of a variety of organosulfur compounds, present in garlic, on hepatic phase II carcinogen detoxification enzymes. We have used the N-methylnitrosourea (NMU)-induced rat mammary tumor model to test the chemopreventive effects of a water-soluble organosulfur constituent derived from aged garlic, S-allylcysteine (SAC). Rats were fed diets supplemented with 666 and 2,000 ppm SAC beginning seven days before initiation with NMU (55 days of age) to termination (18 wk post-NMU), at which time mammary tumors were enumerated. At neither dose did SAC exert an inhibitory effect on any index of tumor development, including incidence, latency, multiplicity, or volume, compared with untreated controls. Weight gains in all groups were similar. Assay of serum SAC levels in supplemented groups indicated that SAC concentrations were beneath the limits of detection of the high-performance liquid chromatography system used. These results contradict previous animal model studies indicating that SAC acts as an inhibitory agent in experimental mammary tumorigenesis; reasons for this discrepancy include the possibility that SAC may exhibit nonlinear dose effects.