Dietary carbohydrates and fat influence radiographic bone mineral content of growing foals

Hydrolyzable carbohydrate intake in horse diets may become excessive when rapidly growing pastures are supplemented with grain-based concentrates. The substitution of fat and fiber for hydrolyzable carbohydrate in concentrates has been explored in exercising horses but not in young, growing horses. Our objective was to compare bone development in foals that were fed pasture and concentrates rich in sugar and starch (corn, molasses) or fat and fiber (corn oil, beet pulp, soybean hulls, oat straw). Forty foals were examined, 20 each in 1994 and 1995. In each year, 10 mares and their foals were fed a corn and molasses supplement (SS) and 10 others were fed a corn oil and fiber supplement (FF). The concentrates were formulated to be isocaloric and isonitrogenous, and mineral content was balanced to complement the pastures and meet or exceed NRC requirements. Dorsopalmar radiographs were taken of the left third metacarpal monthly from birth to weaning and then every other month until 1 yr of age. Bone density was estimated using imaging software and an aluminum stepwedge. Radiographic examination indicated differences in medial, lateral, and central bone mineral content of the metacarpal III. Bone mineral content increased with age, and a plateau was observed during winter. Bone mineral content was lower in weanlings and yearlings fed the FF supplement than in those fed SS. Subjective clinical leg evaluations indicated differences in physitis, joint effusion, and angular and flexural limb deformities in response to age, and possibly to season. Regression analysis indicated positive relationships between bone mineral content and body weight, age, and body measurements. Nutrient and chemical interactions, such as the binding of calcium by fat and fiber, may alter the availability of elements necessary for bone development.

Genetically fluorescent melanoma bone and organ metastasis models

We report here the establishment and metastatic properties of bright, highly stable, green fluorescent protein (GFP) expression transductants of the B16 mouse malignant melanoma cell line and the LOX human melanoma line. The highly fluorescent malignant melanoma cell lines allowed the visualization of skeletal and multiorgan metastases after i.v. injection of B16 cells in C57BL/6 mice and intradermal injection of LOX cells in nude mice. The melanoma cell lines were transduced with the pLEIN expression retroviral vector containing the GFP and neomycin resistance genes. Stable B16F0 and LOX clones expressing high levels of GFP were selected stepwise in vitro in levels of G418 of up to 800 microg/ml. Extensive bone and bone marrow metastases of B16F0 were visualized by GFP expression when the animals were sacrificed 3 weeks after cell implantation. Metastases for both cell lines were visualized in many organs, including the brain, lung, pleural membrane, liver, kidney, adrenal gland, lymph nodes, skeleton, muscle, and skin by GFP fluorescence. This is the first observation of experimental skeletal metastases of melanoma, which was made possible by GFP expression. These models should facilitate future studies of the mechanism and therapy of bone and multiorgan metastasis of melanoma.

Evaluating dizziness

PURPOSE

To conduct a structured literature synthesis on the etiology, prognosis, and diagnostic evaluation of dizziness, and to suggest a primary-care approach to evaluating this symptom.

METHODS

Studies were identified from MEDLINE searches (1966 through 1996) and a manual search of bibliographies from retrieved articles. Two investigators independently abstracted study data.

RESULTS

The most common etiologies for dizziness were peripheral vestibulopathies (35% to 55% of patients) and psychiatric disorders (10% to 25% of patients). Cerebrovascular disease (5%) and brain tumors (<1%) were infrequent. The history and physical examination led to a diagnosis in about 75% of patients. At least 10% of patients eluded diagnosis. Symptoms were usually self-limited and not associated with an increased risk of mortality. The diagnostic testing literature, which was often methodologically flawed, suggested that routine laboratory tests as well as cardiovascular and neurologic testing had a low yield in unselected patients. We could not derive evidence-based guidelines for using specialized vestibular function tests such as electronystagmography.

CONCLUSIONS

Dizziness is usually a benign, self-limited complaint. When a diagnosis can be made, a careful history and physical examination will usually identify the probable cause. Cardiovascular, neurologic, and laboratory testing should be guided by the clinical evaluation. Rigorous studies are needed to determine the accuracy and utility of specialized vestibular testing.

Predicting extracapsular extension of prostate cancer in men treated with radical prostatectomy: results from the population based prostate cancer outcomes study

PURPOSE

We investigated whether clinical information routinely available in community practice could predict extracapsular extension of clinically localized prostate cancer in men undergoing radical prostatectomy.

MATERIALS AND METHODS

We examined prostate cancer outcomes in a population based sample of 3,826 patients with primary prostate cancer in 6 regions of the United States covered by the Surveillance, Epidemiology, and End Results program. Stratified and weighted logistic regression was used to identify predictors of and probabilities for extracapsular extension of clinically localized tumors treated with radical prostatectomy.

RESULTS

Nearly 47% of men undergoing radical prostatectomy had extraprostatic extension. The strongest predictors were elevated prostate specific antigen (PSA) greater than 20 versus less than 4 ng./ml. (odds ratio 5.88, 95% confidence interval 2.90 to 11.15), Gleason score greater than 8 versus less than 6 (1.73, 1.04 to 2.87) and age greater than 70 versus less than 50 years (1.91, 0.98 to 3.70). Ethnicity and region were not associated with increased risk of extraprostatic extension. A nomogram developed from our model predicts extracapsular extension ranging from 24% in men younger than 50 years with PSA less than 4 ng./ml. and a Gleason score of less than 7 to 85% in those 70 years old or older with PSA greater than 20 ng./ml. and a Gleason score of 8 or more. If prostatectomy were limited to patients with less than 60% probability of extraprostatic extension based on the nomogram, 95% of those with organ confined cancers would undergo definitive surgery and 18% of those with extracapsular extension would be spared the morbidity of surgery.

CONCLUSIONS

In a population based analysis of prostate cancer practice patterns PSA, Gleason score and age are clinically useful predictors of extracapsular extension. Although extracapsular extension may be an imperfect predictor of cancer outcomes, our nomogram provides more realistic probabilities for extracapsular extension than those based on institutional series.

Variation in recommendations for cancer screening among primary care physicians in New Mexico

The acceptance of age-appropriate cancer screening as an integral part of primary care has grown among physicians over the past decade. We conducted a mailed survey of all primary care physicians in New Mexico in order to better understand their current cancer screening practices. We found a high rate of self-reported screening, particularly for prostate and colorectal cancer. The screening rates were influenced only slightly by the introduction of evidence-based guidelines, with younger physicians and those with university affiliations more likely to follow recommendations. Female physicians and obstetrician-gynecologists endorsed breast and cervical cancer screening among all age groups and were less likely to follow recommendations for less frequent screening in women as they age. Since a physician's practice beliefs influence his/her attitude toward testing, tailoring education by physician specialty may be more effective than using generic messages in encouraging compliance with the most recent evidence-based guidelines.

Oxygen-dependent chronic obstructive pulmonary disease does not prohibit aortic aneurysm repair

BACKGROUND

Severe oxygen-dependent chronic obstructive pulmonary disease (COPD) is considered by many to be a contraindication to open abdominal aortic aneurysm (AAA) repair. We reviewed our own experience with this patient population.

METHODS

From July 1995 to March 1999, 14 consecutive patients limited by home oxygen-dependent COPD underwent elective open infrarenal AAA repair. Their medical records were reviewed.

RESULTS

The mean aortic aneurysm size was 6.3 cm. The mean PaO2 = 70 mm Hg, PaCO2 = 45 mm Hg, forced expiratory volume in 1 second (FEV1) = 34% of predicted, and forced vital capacity (FVC) = 67% of predicted. All 14 patients were extubated within 24 hours, mean length of hospital stay was 5.9 days, and there were no perioperative deaths.

CONCLUSIONS

Severe home oxygen-dependent COPD is not a contraindication to safe elective open AAA repair.

Alpha-tocopherol supplementation for men with existing coronary artery disease: a feasibility study

BACKGROUND

Recent studies have suggested that alpha-tocopherol supplementation can help reduce the incidence of coronary disease. Our objectives were to determine the feasibility of providing alpha-tocopherol supplements to male veterans with existing coronary artery disease and determine its effects on alpha-tocopherol levels and the susceptibility of low-density lipoprotein (LDL) to oxidation.

METHODS

Fifty-seven percent of 138 coronary disease patients were willing to participate in a placebo-controlled trial -25% were already taking antioxidants. Thirty-nine men were randomly assigned to either 400 mg/day of alpha-tocopherol (n = 27) or placebo (n = 12). alpha-Tocopherol levels and LDL oxidation (measured by formation of thiobarbituric acid-reactive substance) were measured at baseline and at 6 months.

RESULTS

Thirty-three subjects (22 alpha-tocopherol, 11 placebo) completed the study; 3 subjects withdrew after suffering coronary disease events. Supplement compliance exceeded 90% and alpha-tocopherol was well tolerated. The alpha-tocopherol group had a significantly greater mean increase in lipid-adjusted alpha-tocopherol levels (73% vs. -4.6%, P < 0.0001), but oxidized LDL did not change significantly.

CONCLUSIONS

A secondary prevention trial among veterans would be feasible because the rates of enrollment, completion, compliance, and clinical events were high. alpha-Tocopherol supplements did not decrease the susceptibility of LDL to oxidation, suggesting that higher dosages or longer duration of supplementation may be required for secondary prevention.

Efficacy of recombinant methioninase in combination with cisplatin on human colon tumors in nude mice

The present treatment of colon cancer is based on 5-fluorouracil (5-FU). Despite promising results of combining leucovorin or levamisole with 5-FU, the 5-year survival rate of patients with advanced colon cancer has not increased significantly. Colon tumors in vitro have been shown previously to have an elevated requirement for methionine, suggesting a new therapeutic target. In this study, targeting the methionine dependence of colon tumors is effected by recombinant methioninase (rMETase), alone and in combination with cisplatin (CDDP). In vitro results demonstrated that CDDP and rMETase act synergistically on the human colon cancer cell line SW 620, with a combination index (CI) of 0.45, as well as on the human colon cancer cell line Colo 205 with a CI of 0.7. Human colon cancer lines HCT 15, HT 29, Colo 205, and SW 620 growing in nude mice were treated with rMETase to determine an effective dose for depletion of tumor methionine. rMETase at 15 units/g/day for 5 days depleted tumor methionine in all four tumor types to approximately 30% of untreated control. rMETase alone arrested growth of HCT 15 and HT29 in nude mice for 1 week after treatment termination. Colo 205 and SW 620 were partially arrested by rMETase. However, CDDP in combination with rMETase resulted in tumor regression of Colo 205 and growth arrest of SW 620 in nude mice. The ratio of the treated:control group (T:C) tumor weights for Colo 205 was 8% when CDDP was given on day-5, followed by treatment on days 5-9 with rMETase. This treatment schedule resulted in two of the six animals having no detectable tumor when the experiment was terminated on day 16. SW620 was resistant to CDDP alone and only partially sensitive to rMETase alone. However, when SW 620 was treated with rMETase from days-5 to -9 and CDDP on day-5, tumor growth was arrested. The results demonstrate that rMETase used simultaneously in combination with CDDP had significant antitumor efficacy in colon cancer in vitro and in vivo. The data suggest a novel and promising therapeutic approach by targeting the elevated methionine dependence of colon cancer.

Multi-organ metastatic capability of Chinese hamster ovary cells revealed by green fluorescent protein (GFP) expression

Stable high-level green fluorescent protein (GFP)-expressing Chinese hamster ovary cells (CHO) were used to visualize the degree of metastatic behavior of this cell line in nude and SCID mice. A stable GFP high-expression CHO clone, selected in 1.5 microM methotrexate, was injected subcutaneously in nude and severe combined immunodeficient (SCID) mice and implanted orthotopically in the ovary of nude mice. CHO proved to be highly metastatic from both the subcutaneous and orthotopic sites as brightly visualized by GFP fluorescence. High-level GFP-expression allowed the visualization of metastatic tumor in fresh live host tissue in great detail. Metastases were visualized by GFP expression in the lung, pleural membrane, spleen, kidney, ovary, adrenal gland, and peritoneum after orthotopic implantation in nude mice. Metastases were visualized by GFP expression mainly in the lung, pleural membrane after subcutaneous implantation in nude mice. Metastases were visualized in the lung and pleural membrane, liver, kidney, and ovary after subcutaneous implantation in SCID mice. The construction of highly fluorescent stable GFP transfectants of CHO has revealed the multi-organ metastatic capability of CHO cells. CHO has such a high degree of malignancy that it is metastatic from both the orthotopic and subcutaneous transplant sites. This highly malignant GFP-expressing cell-line with multi-organ metastatic affinity should serve as a powerful tool to study tumor-host interaction.

Cellular expression of green fluorescent protein, coupled with high-resolution in vivo videomicroscopy, to monitor steps in tumor metastasis

High resolution intravital videomicroscopy has provided a powerful tool for directly observing steps in the metastatic process, and for clarifying molecular mechanisms of metastasis and modes of action of anti-metastasis therapeutics. Cells previously have been identified in vivo using exogenously added fluorescent labels, limiting observations to a few cell divisions, or by natural markers (e.g. melanin) expressed only by specific cell types. Here we tested the utility of stable green fluorescent protein (GFP)-transfected cells for monitoring and quantifying sequential steps in the metastatic process. Using CHO-K1 cells that stably express GFP, we document the visualization and quantification by intravital videomicroscopy of sequential steps in metastasis within mouse liver, from initial arrest of cells in the microvasculature to the growth and angiogenesis of metastases. Individual, non-dividing cells, as well as micro- and macrometastases could clearly be detected and quantified, as could fine cellular details such as pseudopodial projections, even after extended periods of in vivo growth. We quantified the size distribution of micrometastases and their locations relative to the liver surface using 50 micrometer thick formalin-fixed tissue sections. The data suggest preferential growth and survival of micrometastases near the liver surface. Furthermore, we observed a small population of single cells that persisted over the 11 day observation period, which may represent dormant cells with potential for subsequent proliferation. This study demonstrates the advantages of GFP-expressing cells, coupled with real-time high resolution videomicroscopy, for long-term in vivo studies to visualize and quantify sequential steps of the metastatic process.

Orthotopic transplant mouse models with green fluorescent protein-expressing cancer cells to visualize metastasis and angiogenesis

There have been major efforts in metastasis research in recent years, especially on the role of angiogenesis in the metastatic process. Much of the information in this area has been obtained from model systems that are not representative of clinical cancer. The technique of surgical orthotopic implantation (SOI) has allowed the development of clinically relevant metastatic models of human cancer in immunodeficient rodents such as the nude and SCID mouse. In order to allow direct visualization of the metastatic process, we took advantage of the green fluorescent protein (GFP) of the jellyfish, Aequorea victoria. A series of cancer cell lines have been stably transfected with vectors containing humanized GFP cDNA. To utilize GFP expression for metastasis studies, fragments of subcutaneously growing tumor, which were comprised of GFP-expressing cells, were implanted by SOI in nude mice. Subsequent metastases were visualized in systemic organs by GFP fluorescence in the lung, liver, bones, brain and other organs down to the single-cell level. With this fluorescent tool, we detected and visualized for the first time tumor cells at the microscopic level in fresh viable tissue in their normal host organs even in the live animal. Angiogenesis is readily visualized in the transplanted GFP-expressing tumors in real time in situ in the live animal using simple laparotomy and fluorescent techniques. The results with the GFP-transfected tumor cells, combined with the use of SOI, demonstrate a fundamental advance to visualize and study cancer metastasis and the role of angiogenesis and other factors in the metastatic process.

High-malignancy orthotopic nude mouse model of human prostate cancer LNCaP

BACKGROUND

An animal model of human prostate cancer LNCaP demonstrating high rates of spontaneous metastasis from the orthotopic site after tumor implantation would be very valuable for mechanistic and drug discovery studies. We previously developed microsurgical techniques to implant histologically intact tumor tissues orthotopically in nude mice in order to develop high metastatic mouse models of human cancer.

METHODS

Intact tissue of the androgen-dependent human prostate cancer cell line, LNCaP, was implanted on the ventral lateral lobes of the prostate gland by surgical orthotopic implantation (SOI) in a series of 20 nude mice. Mice were autopsied, and histopathological examination of primary tumors and relevant organs was done to identify and quantitate micrometastasis.

RESULTS

Eighteen of 20 animals transplanted with LNCaP by SOI had tumor growth. Mean primary tumor weight in the prostate was 9.24 g at time of necropsy. Sixty-one percent of the transplanted animals had lymph node metastasis. Forty-four percent had lung metastasis. Mean survival time was 72 days, indicating a high degree of malignancy of the tumor.

CONCLUSIONS

The extensive and widespread lung metastasis as well as lymph node metastasis following orthotopic implantation of LNCaP in nude mice and the short survival time provide a high-malignancy nude model of the LNCaP human prostate tumor.

Development of a high metastatic orthotopic model of human renal cell carcinoma in nude mice: benefits of fragment implantation compared to cell-suspension injection

In this study we compared the metastatic rate of human renal cell carcinoma SN12C in two orthotopic nude mouse models: surgical orthotopic implantation (SOI) of histologically intact tumor tissue and cellular orthotopic injection (COI) of cell suspensions in the kidney. The primary tumors resulting from SOI were larger and much more locally invasive than primary tumors resulting from COI. SOI generated higher metastatic expression than COI. The differences in metastatic rates in the involved organs (lung, liver, and mediastinal lymph nodes) were 2-3 fold higher in SOI compared to COI (P < 0.05). Median survival time in the SOI model was 40 days, which was significantly shorter than that of COI (68 days) (P < 0.001). Histological observation of the primary tumors from the SOI model demonstrated a much richer vascular network than the COI model. Lymph node and lung metastases were larger and more cellular in the SOI model compared to COI. We conclude that the tissue architecture of the implanted tumor tissue in the SOI model plays an important role in the initiation of primary tumor growth, invasion, and distant metastasis. This study directly demonstrates that the implantation of histologically intact tumor tissue orthotopically allows accurate expression of the clinical features of human renal cancer in nude mice. This model should be of value in cancer research and antimetastatic drug discovery for renal cancer, a currently very poorly responding malignancy.

A fluorescent orthotopic bone metastasis model of human prostate cancer

Here, we report a fluorescent spontaneous bone metastatic model of human prostate cancer developed by surgical orthotopic implantation of green fluorescent protein (GFP)-expressing prostate cancer tissue. Human prostate cancer PC-3 cells were transduced with the pLEIN expression retroviral vector containing the enhanced GFP and neomycin resistance genes. Stable GFP high-expression PC-3 clones were selected in vitro with G418, which were then combined and injected s.c. in nude mice. For metastasis studies, fragments of a single highly fluorescent s.c. growing tumor were implanted by surgical orthotopic implantation in the prostate of a series of nude mice. Subsequent micrometastases and metastases were visualized by GFP fluorescence throughout the skeleton, including the skull, rib, pelvis, femur, and tibia The central nervous system, including the brain and spinal cord, was also involved with tumor, as visualized by GFP fluorescence. Systemic organs, including the lung, plural membrane, liver, kidney, and adrenal gland, also had fluorescent metastases. The metastasis pattern in this model reflects the bone and other metastatic sites of human prostate cancer. Thus, this model should be very useful for the study and development of treatment for metastatic androgen-independent prostate cancer.

An ultra-metastatic model of human colon cancer in nude mice

An ultra-high metastatic model of human colon cancer was developed in order to represent highly malignant patient disease for which there is no current model. Surgical orthotopic implantation (SOI) of a histologically intact liver metastasis fragment derived from a surgical specimen of a patient with metastatic colon cancer was initially implanted in the colon, liver and subcutaneously in nude mice. This tumor did not metastasize for the first 10 passages. At the eleventh passage, the tumor exhibited metastasis from the colon to the liver, spleen, and lymph nodes. At this time, two selective passages were carried out by transplanting resulting liver metastases in the nude mice to the colon of additional nude mice. After these two passages, the tumor became stably ultra-metastatic and was termed AC3488UM. One-hundred percent of mice transplanted with AC3488UM with SOI to the colon exhibited local growth, regional invasion, and spontaneous metastasis to the liver, lymph nodes, and spleen. While the maximum size of the primary tumor was 0.9 g, the metastatic liver was over 9 times the weight of the normal liver with the maximum weight of the metastatic liver over 12 g. Liver metastases were detected by the tenth day after transplantation in all animals. Half the animals died of metastatic tumor 25 days after transplantation. Histological characteristics of AC3488UM tumor were poorly differentiated adenocarcinoma of colon. Mutant p53 is expressed heterogeneously in the primary tumor and more homogeneously in the liver metastasis suggesting a possible role of p53 in the liver metastasis. The human origin of AC3488UM was confirmed by positive fluorescence staining for in situ hybridization of human DNA. The AC3488 human colon-tumor model with its ultra-high metastatic capability in each transplanted animal, short latency and a short median survival period is different from any known human colon cancer model and will be an important tool for the study of and development of new therapy for highly metastatic human colon cancer.

Efficacy of new platinum analog DPPE in an orthotopic nude mouse model of human colon cancer

A surgical orthotopic implantation (S.O.I.) model of the human colon cancer cell line Co-3 in nude mice was treated with two doses of the new platinum analogs {Pt(cis-dach) (DPPE).2NO3} and {Pt(trans-dach)(DPPE).2NO3}. The analogs were evaluated for antimetastatic efficacy in comparison to two doses of cisplatinum. Unlike the untreated control group, there were no mesenteric lymph node metastases in the groups treated with the high or low doses of both forms of new DPPE platinum analogs as well as cisplatinum-treated group. However, much more body-weight loss occurred in the cisplatinum-treated group than the DPPE-treated groups. The results obtained with SOI animal model of colon cancer demonstrated both cis- and trans-forms of DPPE had as strong an inhibitory effect on metastasis as that of cisplatinum, but with much less toxicity. Thus the new platinum analogs appears to have promising clinical potential.

A patient-like orthotopic implantation nude mouse model of highly metastatic human ovarian cancer

Clinically relevant animal models of human cancer are important for studies of cancer biology, invasion and metastasis, and for investigating new forms of prognostic diagnosis and therapy. An ovarian tumor line (RMG-1: human clear cell carcinoma of the ovary) previously grown subcutaneously was implanted orthotopically as intact tissue into the ovarian capsule of 22 nude mice. The tumors showed progressive growth at the orthotopic site in all animals. Tumor-associated serum galactosyltransferase (GAT) tended to be positive in all nude -mice. The tumors invaded or metastasized to the contralateral ovary, retroperitoneum, mesentery and peritoneum, and omentum, and metastasized to the subcutaneous tissue, lymph nodes and distant organs including the liver, kidney, pancreas, and diaphragm. In striking contrast, subcutaneous transplantation of this tumor resulted in growth in only 2 of 5 animals with local lymph node and kidney involvement but no retroperitoneal or peritoneal involvement. These findings suggest that orthotopic implantation provides a suitable micro-environment in which ovarian cancer can express its intrinsic clinically-relevant properties. This approach is relevant to the clinical features of ovarian cancer and is thought to be a useful model for studies of therapy for this cancer.

High expression, purification, and properties of recombinant homocysteine alpha, gamma-lyase

Homocysteine alpha,gamma-lyase from the anaerobic protozoan parasite Trichomonas vaginalis has been cloned from genomic DNA using PCR methods and expressed in Escherichia coli with a vector containing the T7 promoter. The recombinant homocysteine alpha,gamma-lyase (rHCYase) is expressed as the major protein in the host E. coli cells. The enzyme was purified to approximately 90% purity using heat treatment at 50 degreesC, precipitation steps with polyethyleneimine, polyethylene glycol 8000, and high sodium chloride, DEAE-Sepharose FF chromatography, and phenyl-Sepharose 6 FF chromatography. The final yield was greater than 50%, which encompassed an approximate 18-fold purification. The enzyme is a homotetramer with a monomer molecular weight of 43K and contains pyridoxal phosphate. The Trichomonas rHCYase is selective for homocysteine with respect to very low cysteinase activity in contrast to the alpha,gamma-lyase from Pseudomonas putida, which has very high cysteinase activity with respect to homocysteine. The T. vaginalis and P. putida alpha,gamma-lyases readily separate on a phenyl-Sepharose 6 FF column with the T. vaginalis enzyme eluting first. rHCYase is stable up to 50 degreesC and active over a pH range of 6-8. These properties of high recombinant expression in E. coli, a simple and effective high-yield purification procedure and high relative specificity for homocysteine with respect to cysteine, make rHCYase a promising candidate to use for the diagnosis of hyperhomocystenemia, which has been demonstrated to be a major risk factor for the onset and mortality of cardiovascular disease of all types.

New sensitive discovery histoculture model for growth-inhibition studies in prostate cancer and BPH

BACKGROUND

A new, total-immersion three-dimensional histoculture (TIH) method was developed to evaluate growth of tissue containing a mixture of benign prostate hyperplasia (BPH) and prostate cancer in vitro.

METHODS

Efficacy of inhibitors, such as genistein, was determined by measuring 3H-thymidine incorporation per microgram protein. Inhibitory effects obtained in TIH were compared to those in sponge-gel supported histoculture (SSH).

RESULTS

3H-thymidine incorporation was 2-5-fold higher in tissue cultured in TIH than in SSH. The average inhibition by genistein at a concentration of 18 JIM was 73% in TIH, vs. 31% in SSH. TIH also appeared to be more sensitive, since the lowest concentration of genistein that significantly inhibited growth of BPH mixed with prostate cancer tissue was 2.3 IJM, while in SSH the lowest concentration was 9.2 F,M. Although the within-assay coefficient of variation (CV) was similar for both TIH and SSH, the between-assay CV was better in TIH.

CONCLUSIONS

These data suggest that TIH can be used as a discovery model for screening and evaluating inhibitors of prostate tissue growth in vitro.