Comparison of proliferating cell nuclear antigen to tritiated thymidine as a marker of proliferating hepatocytes in rats

Immunohistochemical detection of caspase 3 and proliferating cell nuclear antigen in the intestines of dogs naturally infected with parvovirus

Department of Pathology, Faculty of Veterinary Medicine, Burdur Mehmet Akif Ersoy University, Burdur, Turkiye. Canine parvovirus (CPV) causes a contagious and fatal viral disease in dogs characterized by hemorrhagic enteritis. Apoptosis is a programmed cell death and one of the primary markers of this process is caspase 3. Proliferating cell nuclear antigen (PCNA) is also associated with important vital cellular processes. This study was conducted to examine the expressions of caspase 3 and PCNA in the intestinal samples of dogs naturally infected with CPV using immunohistochemical methods. A total of 30 dogs with parvoviral enteritis and five control dogs gut tissues were evaluated for caspase 3 and PCNA expressions. Increased immunoactivities of caspase 3 and PCNA were observed in epithelial, crypt and inflammatory cells in the CPV-infected dogs. Increased expressions of both markers were observed being related to the severity of disease. These results demonstrated the important roles of caspase 3 and PCNA in CPV pathogenesis. These markers may be useful for early diagnosis, estimation of the severity or future treatment strategies of this important disease.

Metronidazole enhances steatosis-related early-stage hepatocarcinogenesis in high fat diet-fed rats through DNA double-strand breaks and modulation of autophagy

Nonalcoholic fatty liver disease is a hepatic disorder with deposition of fat droplets and has a high risk of progression to steatosis-related hepatitis and irreversible hepatic cancer. Metronidazole (MNZ) is an antiprotozoal and antimicrobial agent widely used to treat patients infected with anaerobic bacteria and intestinal parasites; however, MNZ has also been shown to induce liver tumors in rodents. To investigate the effects of MNZ on steatosis-related early-stage hepatocarcinogenesis, male rats treated with N-nitrosodiethylamine following 2/3 hepatectomy at week 3 were received a control basal diet, high fat diet (HFD), or HFD containing 0.5% MNZ. The HFD induced obesity and steatosis in the liver, accompanied by altered expression of Pparg and Fasn, genes related to lipid metabolism. MNZ increased nuclear translocation of lipid metabolism-related transcription factor peroxisome proliferator-activated receptor gamma in hepatocytes, together with altered liver expression of lipid metabolism genes (Srebf1, Srebf2, Pnpla2). Furthermore, MNZ significantly increased the number of preneoplastic liver foci, accompanied by DNA double-strand breaks and late-stage autophagy inhibition, as reflected by increased levels of γ-H2AX, LC3, and p62. Therefore, MNZ could induce steatosis-related hepatocarcinogenesis by inducing DNA double-strand breaks and modulating autophagy in HFD-fed rats.

Enhanced Antitumoral Activity and Photoacoustic Imaging Properties of AuNP-Enriched Endothelial Colony Forming Cells on Melanoma

Near infrared (NIR)-resonant gold nanoparticles (AuNPs) hold great promise in cancer diagnostics and treatment. However, translating the theranostic potential of AuNPs into clinical applications still remains a challenge due to the difficulty to improve the efficiency and specificity of tumor delivery in vivo as well as the clearance from liver and spleen to avoid off target toxicity. In this study, endothelial colony forming cells (ECFCs) are exploited as vehicles to deliver AuNPs to tumors. It is first demonstrated that ECFCs display a great capability to intake AuNPs without losing viability, and exert antitumor activity per se. Using a human melanoma xenograft mouse model, it is next demonstrated that AuNP-loaded ECFCs retain their capacity to migrate to tumor sites in vivo 1 day after injection and stay in the tumor mass for more than 1 week. In addition, it is demonstrated that ECFC-loaded AuNPs are efficiently cleared by the liver over time and do not elicit any sign of damage to healthy tissue.

Effects of Paenibacillus xylanexedens on growth performance, intestinal histomorphology, intestinal microflora, and immune response in broiler chickens challenged with Escherichia coli K88

This study investigated the effects of dietary Paenibacillus xylanexedens ysm1 supplementation on growth performance, intestinal morphology, immune response, and cecal microbiota of broiler chickens challenged with Escherichia coli K88. A total of 320 one-day-old male broiler chicks were randomly allocated to 4 treatments (8 floor pens, 10 birds/pen) including 1) negative control (NC) birds fed a basal diet and not challenged with E. coli K88; 2) positive control (PC) birds fed a basal diet and challenged with of E. coli K88; 3) P. xylanexedens ysm1 treatment (PRO) birds fed a basal diet supplemented with 1 × 109P. xylanexedens ysm1 cfu/kg feed and challenged with E. coli K88; and 4) antibiotic treatment (ANT) birds fed a basal diet supplemented with 20 mg of colistin sulphate/kg of feed and challenged with E. coli K88. The E. coli challenge decreased (P < 0.05) BWG in PC birds compared with the ANT birds on days 21 and 28. The FCR was higher (P < 0.01) in PC birds compared with the NC, PRO, and ANT birds on days 14, 21, and 28. Compared with the NC, PRO, and ANT birds on day 28, PC birds had shorter villi and higher number of goblet cells in both jejunum and ileum (P < 0.001). Irrespective of the dietary treatments, the E. coli challenge reduced the number of PCNA-positive cells in both the jejunum and ileum on day 28. Paenibacillus xylanexedens ysm1 treatment resulted in higher concentration of mucosal sIgA in the jejunum as compared to the other treatment groups on days 14 and 28. The numbers of cecal E. coli were reduced (P = 0.017) in broilers treated with P. xylanexedens ysm1 or antibiotic in comparison with the PC group on day 28. In conclusion, the present study demonstrated that dietary supplementation of this new probiotic bacteria P. xylanexedens ysm1 improved broiler performance by modulating intestinal morphology, enhancing immune response, and reducing the number of E. coli in the cecum.

Spironolactone in Combination with α-glycosyl Isoquercitrin Prevents Steatosis-related Early Hepatocarcinogenesis in Rats through the Observed NADPH Oxidase Modulation

Administration of the diuretic, spironolactone (SR), can inhibit chronic liver diseases. We determined the effects of SR alone or in combination with the antioxidant α-glycosyl isoquercitrin (AGIQ) on hyperlipidemia- and steatosis-related precancerous lesions in high-fat diet (HFD)-fed rats subjected to a two-stage hepatocarcinogenesis model. Rats were fed with control basal diet or HFD, which was administered with SR alone or in combination with an antioxidant AGIQ in drinking water. An HFD increased body weight, intra-abdominal fat (adipose) tissue weight, and plasma lipids, which were reduced by coadministration of SR and AGIQ. SR and AGIQ coadministration also reduced hepatic steatosis and preneoplastic glutathione S-transferase placental form-positive foci, in association with decrease in NADPH oxidase (NOX) subunit p22phox-positive cells and an increase in active-caspase-3-positive cells in the foci. Hepatic gene expression analysis revealed that the coadministration of SR and AGIQ altered mRNA levels of lipogenic enzymes ( Scd1 and Fasn), antioxidant-related enzymes ( Catalase), NOX component ( P67phox), and anti-inflammatory transcriptional factor ( Pparg). Our results indicated that SR in combination with AGIQ had the potential of suppressing hyperlipidemia- and steatosis-related early hepatocarcinogenesis through the reduced expression of NOX subunits.

Deriving and testing of dysplastic murine hepatocytes: A new platform in liver cancer research

Dysplastic hepatocytes (DH) represent altered hepatocytes with potential for malignant transformation. To date, most research on pathways to hepatocarcinogenesis has focused on use of "hepatoma" cell lines derived from hepatocellular carcinoma (HCC). We describe a novel technique for deriving/culturing DH and demonstrate their utility for functional studies in vitro, compared to primary hepatocytes (PH) and HCC. PH and DH were prepared by portal vein collagenase perfusion from C57BL/6J mice. DH were subsequently subjected to FACS. HCC from diethylnitrosamine (DEN)-injected mice were mechanically isolated. Cell cycle analyses were performed by flow cytometry and PCNA immunohistochemistry. To establish utility of DH, we studied pathways of p53 turnover, apoptosis and cell proliferation using pfithrin-α (PFT) and nutlin-3. Like PH, DH were minimally proliferative compared to HCC. Only 30±0.03% of DH were in G₂/M phase versus 51±0.01% of HCC; this difference corroborated with PCNA-immunostaining of dysplastic nodules from DEN-injected mice. In DH and HCC, nutlin-3 suppressed p53 mRNA, induced p53 and mdm2 activation but paradoxically resulted in increased anti-apoptotic and proliferative activity. Primary murine DH display distinctive biological characteristics compared with PH and HCC. As an intermediate cell type to HCC, they offer a new pathobiologically relevant primary cell culture system with which to interrogate the molecular changes in hepatocarcinogenesis.

Proliferating Cell Nuclear Antigen—A Marker for Ovarian Follicle Counts

Enumerating ovarian follicles is an effective way to estimate the extent of ovarian toxicity in female rodents exposed to xenobiotics. Differential follicle counts are useful in safety assessment bioassays and in interspecies extrapolation of ovarian toxicity. Counting the follicles in H&E-stained sections is labor intensive, tedious, and costly. In the present study we demonstrated that in rat formalin-fixed, paraffin-embedded ovary sections follicles of all degrees of maturity can be visualized by the use of antibody directed against proliferating cell nuclear antigen (PCNA). Follicles are easily distinguished from ovarian background with the ability to detect and identify primordial follicles being enhanced. This translates into a significant decrease in variability of follicle counts, labor, and cost. Specifically, variability dropped from 11% to 0.2%, the counting time was reduced by 46%, and the cost by 48%.

Immunohistochemical (Ki-67) study of endometrial maturation in mice after use of phosphodiesterase type 5 inhibitor

BACKGROUND

Uterine receptivity for the implantation is a complicated process, that ovarian factors (hormonal), endometrium and embryo simultaneously are involved in this phenomenon. A successful implantation needs appropriate development of the endometrium. Furthermore, embryo must be capable of reacting with the endometrium and producing suitable adhesion molecules. This study aimed to examine one of endometrial maturation indices in mice before implantation, i.e., proliferation of stromal cells.

MATERIALS AND METHODS

A total of 40 adult female mice were divided into four groups: Control, gonadotropin, gonadotropin + progesterone, and gonadotropin + sildenafil citrate. The three experimental groups were first injected 7.5 IU of human chorionic gonadotropin (HCG) and then 7.5 IU of human menopausal gonadotropin (HMG). Then, every two female mice were placed in a cage with a male mouse for mating. Two groups were injected 1 mg of progesterone and 3 mg/kg of sildenafil citrate at intervals of 24, 48, and 72 h after injection of HMG. After 96 h, all the mice were killed, and their uterine samples subjected to tissue passage and prepared for analysis. Immunohistochemical method, Ki-67, and stromal mitotic cell count were used in this study.

RESULTS

Our observations in all groups showed changes in the luminal epithelium. ANOVA analysis Ki-67-positive stromal cells among all groups were not statistically significant.

CONCLUSION

The results showed that administration of HMG and HCG following that of progesterone and sildenafil citrate could change the indices of endometrial maturation, and they were not involved in the phase immediately before implantation in stromal mitotic index.

Caffeine increases Nr1i3 expression and potentiates the effects of its ligand, TCPOBOP, in mice liver

<p>Caffeine is one of the world's most consumed substances. It is present in coffee, green tea and guarana, among others. The xenobiotic-sensing nuclear receptor subfamily 1, group I, member 3 (Nr1i3), also known as the Constitutive Androstane Receptor (Car) is a key regulator of drug metabolism and excretion. No consistent description of caffeine effects on this receptor has been described. Thus, to unravel the effects of caffeine on this receptor, we performed experiments in mice. First, C57Bl/6 mice that were treated daily with caffeine (50 mg/kg) for 15 days presented a slight but significant increase in Nr1i3 and Cyp2b10 gene expression. A second experiment was then performed to verify the effects of caffeine on TCPOBOP (1,4-<italic>bis</italic>-[2-(3,5-dichloropyridyloxy)]benzene, 3,3′,5,5′-tetrachloro-1,4-<italic>bis</italic>(pyridyloxy)benzene), the most potent agonist known for mice Nr1i3. Interestingly, caffeine potentiated TCPOBOP pleiotropic effects in mice liver, such as hepatomegaly, hepatotoxicity, hepatocyte proliferation and loss of cell-to-cell communication through gap junctions. In addition, caffeine plus TCPOBOP treatment increased liver gene expression of Nr1i3 and Cyp2b10 comparing with only caffeine or TCPOBOP treatments. Together, these results indicate that caffeine increases the expression of Nr1i3 in mice liver, although at this point it is not possible to determine if Nr1i3 directly or indirectly mediates this effect.</p>

Germinated brown rice and its bioactives modulate the activity of uterine cells in oophorectomised rats as evidenced by gross cytohistological and immunohistochemical changes

Background

Germinated brown rice (GBR) is gaining momentum in the area of biomedical research due to its increased use as a nutraceutical for the management of diseases. The effect of GBR on the reproductive organs of oophorectomised rats was studied using the gross, cytological, histological and immunohistochemical changes, with the aim of reducing atrophy and dryness of the genital organs in menopause.

Methods

Experimental rats were divided into eight groups of six rats per group. Groups 1, 2 and 3 (sham-operated (SH), oophorectomised without treatment (OVX) and oophorectomised treated with 0.2 mg/kg oestrogen, respectively) served as the controls. The groups 4,5,6,7 and 8 were treated with 20 mg/kg Remifemin, 200 mg/kg of GBR, ASG, oryzanol and GABA, respectively. All treatments were administered orally, once daily for 8 weeks. Vaginal smear cytology was done at the 7^th week on all the rats. The weight and dimensions of the uterus and vagina were determined after sacrifice of the rats. Uterine and vaginal tissues were taken for histology and Immunohistochemical examinations.

Results

GBR and its bioactives treated groups significantly increased the weight and length of both the uterus and the vagina when compared to Oophorectomised non-treated group (OVX-non-treated) (p < 0.05). Significant changes were observed in the ratio of cornified epithelial cells and number of leucocytes in the vaginal cytology between the oophorectomised non-treated and treated groups. There was also an increase in the luminal and glandular epithelial cells activity in the treated compared with the untreated groups histologically. Immunohistochemical staining showed specific proliferating cell nuclear antigen (PCNA) in the luminal and glandular epithelium of the treated groups, which was absent in the OVX-non-treated group. GBR improved the length and weight of the uterus and also increased the number of glandular and luminal cells epithelia of the vagina.

Conclusion

GBR and its bioactives could be a potential alternative in improving reproductive system atrophy, dryness and discomfort during menopause.

Recovery of the Cell Cycle Inhibition in CCl(4)-Induced Cirrhosis by the Adenosine Derivative IFC-305

Introduction. Cirrhosis is a chronic degenerative illness characterized by changes in normal liver architecture, failure of hepatic function, and impairment of proliferative activity. The aim of this study is to know how IFC-305 compound induces proliferation of the liver during reversion of cirrhosis. Methods. Once cirrhosis has been installed by CCl(4) treatment for 10 weeks in male Wistar rats, they were divided into four groups: two received saline and two received the compound; all were euthanized at 5 and 10 weeks of treatment. Liver homogenate, mitochondria, and nucleus were used to measure cyclins, CDKs, and cell cycle regulatory proteins PCNA, pRb, p53, E2F, p21, p27, HGF, liver ATP, and mitochondrial function. Results. Diminution and small changes were observed in the studied proteins in the cirrhotic animals without treatment. The IFC-305-treated rats showed a clear increase in most of the proteins studied mainly in PCNA and CDK6, and a marked increased in ATP and mitochondrial function. Discussion/Conclusion. IFC-305 induces a recovery of the cell cycle inhibition promoting recovery of DNA damage through the action of PCNA and p53. The increase in energy and preservation of mitochondrial function contribute to recovering the proliferative function.

G1 cell cycle arrest signaling in hepatic injury after intraperitoneal sepsis in rats

OBJECTIVE AND DESIGN

Hepatocytes emerge from a quiescent state into a proliferative state to recover from septic injury. We hypothesize that hepatocyte cell cycle regulation after sepsis potentially contributes to the recovery of liver function.

METHODS

An animal model of sepsis was induced by cecal ligation and puncture (CLP) in rats. At serial time points after CLP, hepatocyte expression of p21, P53, cyclin D1, cyclin E, CDK2, CDK4 and PCNA was determined by immunoblot analysis, and the DNA content of isolated hepatocytes was analyzed using flow cytometry.

RESULTS

Sepsis-induced liver injury of rats was associated with G1 cell cycle arrest. Recovery of liver function was related to cell cycle progression 48 h after CLP. The upregulation of p53 and p21 correlated with G1 cell arrest 48 h after CLP. The upregulation of cyclin D1/CDK4 and cyclin E/CDK2 also correlated with the G1/S transition 48 h after CLP, resulting in PCNA expression.

CONCLUSIONS

The data suggests that G1 cell cycle arrest and p53, p21, CDKs, cyclins and PCNA expression may be involved in the injury/recovery of liver function after intraperitoneal sepsis.

C/EBPα expression is downregulated in human nonmelanoma skin cancers and inactivation of C/EBPα confers susceptibility to UVB-induced skin squamous cell carcinomas

Human epidermis is routinely subjected to DNA damage induced by UVB solar radiation. Cell culture studies have revealed an unexpected role for C/EBPα (CCAAT/enhancer-binding protein-α) in the DNA damage response network, where C/EBPα is induced following UVB DNA damage, regulates the G(1) checkpoint, and diminished or ablated expression of C/EBPα results in G(1) checkpoint failure. In the current study we observed that C/EBPα is induced in normal human epidermal keratinocytes and in the epidermis of human subjects exposed to UVB radiation. The analysis of human skin precancerous and cancerous lesions (47 cases) for C/EBPα expression was conducted. Actinic keratoses, a precancerous benign skin growth and precursor to squamous cell carcinoma (SCC), expressed levels of C/EBPα similar to normal epidermis. Strikingly, all invasive SCCs no longer expressed detectable levels of C/EBPα. To determine the significance of C/EBPα in UVB-induced skin cancer, SKH-1 mice lacking epidermal C/EBPα (CKOα) were exposed to UVB. CKOα mice were highly susceptible to UVB-induced SCCs and exhibited accelerated tumor progression. CKOα mice displayed keratinocyte cell cycle checkpoint failure in vivo in response to UVB that was characterized by abnormal entry of keratinocytes into S phase. Our results demonstrate that C/EBPα is silenced in human SCC and loss of C/EBPα confers susceptibility to UVB-induced skin SCCs involving defective cell cycle arrest in response to UVB.

Protective effects of Ginkgo biloba against rat liver carcinogenesis

Ginkgo biloba (EGb) has been proposed as a promising candidate for cancer chemoprevention and has shown protective effects on the liver against chemically induced oxidative injury and fibrosis. The potential beneficial effects of EGb were investigated in two rat liver carcinogenesis bioassays induced by diethylnitrosamine (DEN). In a short-term study for anti-initiating screening, male Wistar rats were fed a basal diet or supplemented diet with 500 or 1000 ppm EGb and initiated 14 days later with a single dose of DEN (100 mg/kg i.p.). The respective groups were killed 24h or 2 weeks after DEN-initiation. Liver samples were collected for the analysis of proliferating cell nuclear antigen (PCNA), transforming growth factor alpha (TGF-alpha), p53, apoptosis and induction of single hepatocytes and minifoci positive for the enzyme glutathione S-transferase P-form (GST-P). In a medium-term study for anti-promoting screening, the animals received a single dose of DEN (200 mg/kg i.p.) and, 2 weeks later, were fed a basal diet or supplemented diet with 500 or 1000 ppm EGb for 6 weeks. All animals underwent 70% partial hepatectomy (PH) at week 3 and killed at week 8. Liver samples were collected to analyze development of preneoplastic foci of altered hepatocytes (FAH) expressing GST-P. In the short-term study, pretreatment of rats with 1000 ppm EGb significantly reduced the rates of cell proliferation, apoptosis and p53, TGF-alpha immunoreactivity and the number of GST-P-positive hepatocytes. In the medium-term study, EGb treatment during the post-initiation stage failed to reduce the development of DEN-induced GST-P-positive foci. Thus, EGb presented inhibitory actions during initiation but not promotion of rat liver carcinogenesis induced by DEN.

Increased islet neogenesis without increased islet mass precedes autoimmune attack in diabetes-prone rats

We reported previously that young BioBreeding diabetes-prone (BBdp) rats display increased neogenic extra-islet insulin+ clusters (EICs, <4 insulin+ cells) without an increase in beta-cell mass. Therefore, we investigated the possibility that abnormal islet expansion occurs in BBdp rats before the appearance of islet inflammation. Islet expansion was analyzed in pancreata from 14 to 45 day BBdp and control (BioBreeding control, BBc) rats using immunohistochemistry, morphometry, laser capture microdissection and reverse transcriptase-PCR. mRNA expression for Neurogenin-3, a developmental marker of endocrine progenitors, was three-fold greater in EIC of weanling BBdp and BBc rats compared with islet cells. With increasing age (14-30 days), Neurogenin-3 expression decreased in EIC and increased in islets. In BBdp rats, EIC number and beta-cell proliferation within EIC was greater compared with BBc animals; apoptosis did not differ. The area of small and medium islets in BBdp rats was greater than BBc rats between 14 and 30 days, but this did not result in increased total islet area or beta-cell mass. In addition, the number and area of very large islets was low at 45 days. The frequency of proliferating beta-cells decreased with increasing islet size in BBdp but was constant in BBc rats. Cell cycle analysis of islets revealed more G1 cells and fewer G2 cells in BBdp rats. The ratio of cyclinD2/Cdkn1a, genes that respectively promote or inhibit cell cycle progression, was decreased in BBdp islets. These results suggest that despite increased islet neogenesis, the capacity for islet expansion in diabetes-prone rats is compromised possibly due to decreased proliferative capacity with increasing islet size associated with a partial block at the G1/S cell cycle boundary in islet cells.

Pifithrin-alpha induced p53 inhibition does not affect liver regeneration after partial hepatectomy in mice

BACKGROUND/AIMS

Beside its well-known function as tumour suppressor gene, p53 is supposed to positively regulate cell division and cell differentiation. Because hepatocyte proliferation has been reported to be reduced by blockade of p53 function in vitro, we examined in the present study the impact of p53 inhibition on hepatocyte proliferation in vivo.

METHODS

Mice treated with either pifithrin-alpha (PFT), a p53-inactivating agent, or the equivalent volume of vehicle, were subjected to 70% hepatectomy. In addition to assessment of liver mass restitution we examined p53 and p21 protein expression as well as PCNA expression and BrdU incorporation by using Western blot and immunohistochemical techniques. Extent of apoptosis was assessed by TUNEL assay.

RESULTS

PFT lowered nuclear but not cytoplasmic p53, and did not inhibit protein expression of regeneration-associated p21. PCNA protein expression as well as PCNA and BrdU immunohistochemistry did not differ between regenerating livers of either PFT- or vehicle-treated animals. Moreover, TUNEL analysis of regenerated liver tissue revealed comparable numbers of apoptotic cells in both groups.

CONCLUSIONS

Pharmacological inhibition of p53 did not impair liver regeneration in mice, implying that p53 is functionally redundant in that p53-independent pathways compensate for the blockade of p53 and sufficiently support the process of hepatocyte replication in liver regeneration.

Distribution of the stem cells (neoblasts) in the planarian Dugesia japonica

It has been postulated that the high regeneration ability of planarians is supported by totipotent stem cells, called neoblasts. There have been a few reports showing the distribution of neoblasts in planarians. However, the findings were not completely consistent. To determine the distribution of neoblasts, we focused on proliferating cell nuclear antigen (PCNA), which is present in proliferative cells. We cloned and sequenced the cDNA of PCNA from the planarian Dugesia japonica and produced an antiserum recognizing the gene product. X-ray irradiation caused rapid loss of all PCNA-positive cells and loss of the neoblasts (which were morphologically defined by the presence of the chromatoid body), strongly suggesting that all PCNA-positive cells were true neoblasts. Using the antiserum, we were successful in identifying the neoblasts more clearly than any previous work. In addition to their dispersed distribution in the dorsal and ventral mesenchyme, the neoblasts were distributed as clusters along the midline and bilateral lines in the dorsal mesenchyme. We also examined the behavior of the neoblasts after decapitation. Decapitation did not seem to affect the migration of neoblasts far from the wound. We demonstrated here that DjPCNA is a powerful tool for identifying planarian neoblasts.

The use of proliferating cell nuclear antigen immunohistochemistry with a unique functional marker to detect postnatal neurogenesis in paraffin-embedded sections of the mature pig brain

Until recently, evidence supporting postnatal neurogenesis was controversial. Much of the debate has centered on the identification of the dividing cells as neurons versus glia. Because neurogenesis has become a well-documented phenomenon, there is a need for reliable protocols to identify recently divided neurons in a wide range of situations. To facilitate the investigation of postnatal neurogenesis of magnocellular neurons in the pig hypothalamus, a sequential immunohistochemical staining technique was developed for use on serial sections of paraffin-embedded tissue. Proliferating neurons were labeled using mouse-derived monoclonal antibodies to detect proliferating cell nuclear antigen (PCNA) and vasopressin (VP). PCNA, a nuclear protein essential for cell division, identifies recently divided cells in the brains of healthy animals. VP is a unique functional marker for a mature neuron. The presence of a cell with VP positive cytoplasm and a PCNA positive nucleus demonstrates the presence of a VP-producing neuron that has recently divided. This protocol allowed us to safely and accurately label recently proliferated neurons in the mature pig hypothalamus and can be used on archived tissue. This data can be used for further morphometric analysis, as serial sectioning allows for three-dimensional reconstruction of hypothalamic nuclei.

Mammary gland morphogenesis is enhanced by exposure to flaxseed or its major lignan during suckling in rats

The exposure of rats to 10% flaxseed (FS) or an equivalent level of its major lignan, secoisolariciresinol diglucoside (SDG), during suckling enhances mammary gland differentiation, which protects against mammary carcinogenesis at adulthood. We determined whether this diet-induced mammary gland differentiation is mediated through the estrogenic pathway via epidermal growth factor receptor (EGFR) and estrogen receptor (ER) signaling. Rats were fed the AIN-93G basal diet (BD) from day 7 of pregnancy until delivery and then randomized to consume BD, FS, or SDG during lactation. After weaning, female offspring were fed BD throughout the experiment. At postnatal day (PND) 21 and the proestrus phase on PND 49-51, mammary glands of offspring were analyzed for morphology, cell proliferation, and expression of EGFR, epidermal growth factor (EGF), transforming growth factor-alpha, ER-alpha, and ER-beta. At PND 21, compared with the BD control, the number of terminal end buds (TEBs) and terminal ducts were increased by FS, whereas mammary epithelial cell proliferation was increased by both FS and SDG, suggesting that mammary morphogenesis was enhanced. Epithelial EGFR and stromal fibroblast EGF were increased by SDG, whereas epithelial ER-beta was decreased by FS. Conversely, at PND 49-51, a lower number of TEBs but a higher ratio of lobules to TEBs with decreased expression of EGFR or EGF was observed in both treatment groups. EGFR expression was positively associated with EGF expression and cell proliferation in TEB epithelium at PND 21. Urinary lignans of lactating dams were related to their offspring's indices of mammary gland development. In conclusion, exposure to FS or SDG during suckling enhanced mammary gland morphogenesis by modulation of EGFR and ER signaling, which led to more differentiated mammary glands at PND 49-51. The physiological outcomes of FS and SDG were similar, which suggests that SDG is partly responsible for the mammary gland differentiation effect.

Evaluation of cell proliferation in rat tissues with BrdU, PCNA, Ki-67(MIB-5) immunohistochemistry and in situ hybridization for histone mRNA

The standard method for assessment of cell proliferation in paraffin-embedded tissue sections is 5-bromodeoxyuridine (BrdU) immunohistochemistry (IHC). BrdU can be administered to laboratory animals via IP injections, is readily incorporated into nuclei during the DNA synthetic phase of the cell cycle, and is detected with an anti-BrdU antibody. This method has several disadvantages, and an accurate method for evaluation of proliferative activity that can substitute for BrdU IHC, when necessary, is of great interest to investigators. Alternative methods for detection of proliferating cells in tissue sections are proliferating cell nuclear antigen (PCNA) IHC, Ki-67 IHC, and in situ hybridization (ISH) for histone mRNA. To determine the optimal choice, we analyzed the correlation of anti-PCNA, anti-Ki-67(MIB-5), and histone mRNA labeling indices (LIs) with anti-BrdU LI in rat highly replicative (renewing) tissues. The correlation between anti-BrdU and histone mRNA LIs, as well as the correlation between anti-BrdU and anti-Ki-67 LIs, was statistically significant. There was no significant correlation between anti-BrdU and anti-PCNA LIs. These results suggest that both ISH for histone mRNA and IHC with MIB-5 are preferable techniques for assessment of cell proliferation in rat paraffin-embedded renewing tissues compared to PCNA IHC. They can substitute for BrdU IHC when necessary.

Chemoprevention of preneoplastic liver foci development by dietary mushroom Agaricus blazei Murrill in the rat

The chemopreventive potential of an Agaricus blazei (Ab) Murrill mushroom meal was investigated in a medium-term rat liver carcinogenesis assay. Male Wistar rats initiated for hepatocarcinogenesis with diethylnitrosamine (DEN, 200 mg/kg i.p.) were fed during a 6-week period with the dry powdered mushroom strains Ab 29 or 26, each one with opened (OB) or closed basidiocarp (CB), mixed at 10% level in a basal diet. All experimental animals and controls were subjected to partial hepatectomy at week 3 and killed at week 8. Chemopreventive activity of the mushroom meal was observed for the Ab 29 (OB and CB) and Ab 26 (CB) strains in terms of the number of putative preneoplastic altered foci of hepatocytes which express either the enzyme glutathione S-transferase, placental form (GST-P+) or the transforming growth factor-alpha, and for the Ab 29 (OB) and Ab 26 (CB) strains on the size of GST-P+ foci. This was associated with inhibition of foci cell proliferation in the animals fed the Ab 29 (OB) and Ab 26 (CB) strains. The results suggest that the protective influence of the Ab meal against the DEN potential for rat liver carcinogenicity depends on both the strain and period of mushroom harvest.

Mechanisms of promotion and progression of preneoplastic lesions in hepatocarcinogenesis by DDT in F344 rats

Time-related changes in potential factors involved in hepatocarcinogenesis by DDT were investigated in a 4-week and a 2-year feeding studies of p,p'-DDT with F344 rats. In the 4-week study with males at doses of 50, 160, and 500 ppm, cell proliferation and gap junctional intercellular communication (GJIC) were examined after 1, 2, 3, 7, 14, and 28 days. Cell proliferation was enhanced within 3 days at any dose level, but returned to normal after 7 days, whereas GJIC was inhibited throughout the study. In the 2-year study with both sexes at doses of 5, 50, and 500 ppm, cell proliferation, GJIC, enzyme induction, and oxidative stress were investigated after 26, 52, 78, and 104 weeks. Males and females showed an inhibition of GJIC and increases in P450 isozymes (CYP2B1 and CYP3A2) in a dose-dependent manner at all time points, but no significant change in cell proliferation. Lipid peroxide for males at 50 and 500 ppm and 8-hydroxydeoxyguanosine for both sexes at 500 ppm were elevated throughout the study. Histologically, eosinophilic foci and hepatocellular adenomas increased in males at 50 ppm and both sexes at 500 ppm. Hepatocellular carcinomas also developed in males at 500 ppm. These results indicate that DDT may induce eosinophilic foci as a result of oxidative DNA damage and leads them to neoplasms in combination with its mitogenic activity and inhibitory effect on GJIC. Oxidative stress could be a key factor in hepatocarcinogenesis by DDT.

Influence of aqueous extract of Agaricus blazei on rat liver toxicity induced by different doses of diethylnitrosamine

The modifying potential of prior administration of an aqueous extract of the mushroom Agaricus blazei Murrill (Agaricaceae) (Ab) on hepatotoxicity induced by different doses of diethylnitrosamine (DEN) in male Wistar rats was evaluated. During 2 weeks, animals of groups G3 (Ab+DEN(50)), G5 (Ab+DEN(100)), G7 (Ab+DEN(200)), and G8 (Ab-treated) were treated with the A. blazei through drinking water. After this period, groups G2 (DEN(50)), G3 (Ab+DEN(50)), G4 (DEN(100)) G5 (Ab+DEN(100)), G6 (DEN(200)), and G7 (Ab+DEN(200)) were given a single i.p. injection of 50, 100 and 200 mg/kg of DEN, respectively, while groups G1 (non-treated) and G8 (Ab-treated) were treated with 0.9% NaCl only. All animals were killed 48 h after DEN or NaCl treatments. The hepatocyte replication rate was estimated by the index of the proliferating cell nuclear antigen (PCNA) positive hepatocytes and the appearance of putative preneoplastic hepatocytes through expression of the enzyme glutathione S-transferase placental form (GST-P). After DEN-treatment, ALT levels, PCNA labeling index, and the number of GST-P positive hepatocytes were lower in rats that received A. blazei treatment and were exposed to 100 mg/kg of DEN. Our findings suggest that previous treatment with A. blazei exerts a hepatoprotective effect on both liver toxicity and hepatocarcinogenesis process induced by a moderately toxic dose of DEN.

Bioavailability and efficacy of antisense morpholino oligomers targeted to c-myc and cytochrome P-450 3A2 following oral administration in rats

Antisense phosphorodiamidate Morpholino oligomers (PMO) are resistant to degradation by cellular hydrolases, DNases, RNases, and phosphodiesterases, but remain sensitive to prolonged exposure to low pH. The present studies evaluate the oral fractional bioavailability, stability, and efficacy of two distinct PMO sequences targeted to c-myc and cytochrome P-450 (CYP) 3A2. The c-myc antisense 20-mer, AVI-4126 (5'-ACGTTGAGGGGCATCGTCGC-3'), slowed the regenerative process in the rat liver after a 70% partial hepatectomy (PH). Rats were administered 3.0 mg/kg AVI-4126 in 0.1 mL saline via a bolus intravenous injection or in 0.5 mL sterile phosphate-buffered saline via gavage immediately following PH. The areas under the plasma concentration versus time curves revealed a fractional oral availability of 78.8% over a period of 10 min through 24 h. Immunoblot analysis of liver tissue from rats treated orally with AVI-4126 demonstrated a sequence-specific reduction in the target protein c-Myc, as well as secondary proliferation markers: proliferating cell nuclear antigen (PCNA), cyclin D1, and p53. The CYP3A2 antisense 22-mer AVI-4472 (5'-GAGCTGAAAGCAGGTCCATCCC-3') caused a sequence-dependent reduction of approximately five-fold in the rat liver CYP3A2 protein levels and erythromycin demethylation activity in 24 h following oral administration at a dose of 2 mg/kg. It is concluded that oral administration of PMOs can inhibit c-myc and CYP3A2 gene expression in rat liver by an antisense-based mechanism of action. These studies highlight the potential for development of PMOs as orally administered therapeutic agents.

P-Nitrobenzoic acid alpha2u nephropathy in 13-week studies is not associated with renal carcinogenesis in 2-year feed studies

The objective of this study was to characterize the renal toxicity and carcinogenicity of p-nitrobenzoic acid in F344 rats. Dose levels in 13-week and 2-year studies ranged from 630-10,000 ppm and 1,250-5,000 ppm, respectively. At 13 weeks, renal lesions included minimal to mild hyaline droplet accumulation in male rats and karyomegaly in male and female rats. At 2 years, renal lesions included proximal tubule epithelial cell hyperplasia in male rats and oncocytic hyperplasia in high-dose male and female rats, and a decreased severity of nephropathy in males and females. The hvaline droplets in renal tubular epithelial cells of male rats at 13 weeks were morphologically similar to those described in alpha2u-globulin nephropathy. Using immunohistochemical methods, alpha2u-globulin accumulation was associated with the hyaline droplets. In addition, at 13 weeks, cell proliferation as detected by PCNA immunohistochemistry was significantly increased in males exposed to 5,000 and 10,000 ppm when compared to controls. Cytotoxicity associated with alpha2U-globulin nephropathy such as single-cell necrosis of the P2 segment epithelium or accumulation of granular casts in the outer medulla did not occur in the 13-week study. In addition, chronic treatment related nephrotoxic lesions attributed to accumulation of alpha2u-globulin such as linear foci of mineralization within the renal papilla, hyperplasia of the renal pelvis urothelium and kidney tumors were not observed. Although there was histologic evidence of alpha2u-globulin accumulation in male rats at 13 weeks, the minimal severity of nephropathy suggests that the degree of cytotoxicity was below the threshold, which would contribute to the development of renal tumors at 2 years.

Cell response endpoints enhance sensitivity of the immature mouse uterotropic assay

Outbred immature CD-1 mice were subcutaneously (s.c.) injected once on postnatal day 17 or on postnatal days 17, 18, and 19 with 17beta-estradiol, diethylstilbestrol, tamoxifen, 4-hydroxytamoxifen, methoxychlor, the methoxychlor metabolite HPTE, nonylphenol, o,p'-DDT, endosulfan, or kepone over a wide dose range (0.1 to 1,000,000 microg/kg). On the day following the last injection, uterine weight/body weight ratios were determined and uterine tissues processed for histologic examination. All compounds except endosulfan and kepone increased uterine wet weight compared to vehicle controls; however, the dose response curve and magnitude of response varied depending on the compound. Choosing the maximum wet weight dose for each compound, uterine tissue was evaluated for epithelial cell height, epithelial and stromal cell proliferation, endometrial gland number, and induction of estrogen-inducible proteins lactoferrin and complement C3. All compounds elicited estrogen-responsive changes in these endpoints that were individually more sensitive than uterine weight alone. We conclude that these endpoints enhance the sensitivity of the uterotropic bioassay.

Age-related cell proliferation and apoptosis in the kidney of male Fischer 344 rats with observations on a spontaneous tubular cell adenoma

Cell proliferation rate and apoptosis were examined in archival kidneys from young, middle-aged, and old male F344 rats. Immunohistochemical expression of proliferating cell nuclear antigen (PCNA) and apoptosis were quantified in the same cell populations of the proximal tubule epithelium. A total of 79 kidneys from 40 rats were examined. There was a progressive increase in cell proliferation rates in rats from 4 and 6-10 months of age. In 23-month-old rats, proliferative activity appeared to be reduced. No age-related variations in apoptotic indices were found. One of the 16 rats aged 23 months had a tubular cell adenoma. In the tumor-affected kidney, cell proliferation rate was dramatically higher than in the contralateral kidney as well as in all the other kidneys examined. This high proliferative activity was not balanced by variation in cell death.

Two-dimensional electrophoresis of liver proteins: characterization of a drug-induced hepatomegaly in rats

Two-dimensional electrophoresis (2-DE) of liver proteins was applied to further characterize an unusual drug-induced increase in hepatocellular rough endoplasmic reticulum (RER) in Sprague-Dawley rats given a substituted pyrimidine derivative. Absolute liver weights of drug-treated rats (9.9 +/- 0.4 g) increased above vehicle-treated controls (7.2 +/- 0.2 g) by 37%. Light microscopy revealed diffuse granular basophilia of the hepatocellular cytoplasm, uncharacteristic of hepatocytes and suggested cells rich in ribosomes, which was confirmed by electron microscopy. Immunostaining for cell proliferation, viz., 5-bromo-2'-deoxyuridine (BrdU) and proliferating cell nuclear antigen (PCNA), indicated marked hepatocellular proliferative activity. 2-DE of solubilized liver using an ISO-DALT gel system indicated significant (p<0.001) quantitative changes in at least 17 liver proteins (12 increased, 5 decreased) compared to controls. The protein with the largest increase was homologous to acute-phase reactant, contrapsin-like protein inhibitor-6. Other markedly upregulated proteins were methionine adenosyltransferase, a catalyst in methionine/ATP metabolism and mitochondrial HMG-CoA synthase, involved in cholesterol synthesis. The complementary strategies of 2-DE coupled either with database spot mapping or protein isolation and amino acid sequencing successfully identified a subset of proteins from xenobiotic-damaged rodent livers, the expression of which differed from controls. However, the current bioinformatics platform for rodent hepatic proteins and limited knowledge of specific protein functionality restricted application of this proteomics profile to further define a mechanistic basis for this unusual hepatotoxicity.

Changes associated with delay of mammary cancer by retinoid analogues in transgenic mice bearing c-neu oncogene

Breast cancer is one of the common cancers and is a leading cause of cancer mortality in women. The TG.NK transgenic mouse line on FVB strain background expresses the c-neu oncogene under the control of a MMTV promoter in mammary tissue and appears to be a useful animal model for evaluation of strategies to delay or prevent mammary cancer. Fiber-rich nonpurified diet (NTP-2000) and some retinoid analogues have delayed mammary cancer in the TG.NK model. Four week old hemizygous TG.NK female mice with MMTV/c-neu (erbB2) activated oncogene were fed NTP-2000 diet containing the retinoid analogue 4-hydroxyphenylretinamide (4-HPR) at 7 mmol/kg or the arotinoid Ro 40-8757 at 1.5 and 2.5 mmol/kg for 26 weeks. The 4-HPR at 7 mmol/kg diet delayed the development of palpable tumors up to 24 weeks, but by 26 weeks, the incidence markedly increased and was closer to the NTP-2000 diet control group. However, the 4-HPR diet markedly decreased the average weight of the tumors at 26 weeks with no decrease in multiplicity. The 4-HPR also caused significant increase in liver weights without an effect on body weight. Arotinoid Ro 40-8757 caused marked decrease in the number and branching of mammary ducts, and inhibited mammary tumor development with significant decrease in the incidence, multiplicity, and tumor weights compared to the NTP-2000 diet control. Arotinoid also caused a significant dose-related increase in liver weights without a significant effect on body weights. At the doses tested, the arotinoid but not 4-HPR decreased the circulating levels of IGF-1. However, there was no association between the IGF-1 levels and the size, incidence, or absence of tumors when evaluated for any treatment group or for all mice in the study irrespective of treatment. The oncogene erbB2 (c-neu) and the growth factor EGF expression were more prominent in the small tumors of the mice treated with arotinoid than in the larger tumors of the control group. PCNA staining was observed in areas where there was high erbB2 and EGF staining. The delay in onset of mammary tumors by the above retinoid analogues may be related to the delay in development of mammary glands.

Effect of turkey (Meleagridis gallopavo) breeder hen age and egg size on poult development. 2. Intestinal villus growth, enterocyte migration and proliferation of the turkey poult

Villus growth, enterocyte migration and proliferation were measured in the small intestine of poults (Meleagridis gallopavo) to determine if hen age and/or egg size influences these characteristics during the first week after hatching. At hatching, distal jejunal villi were 22.8 microns longer in poults from the older (48 weeks) versus the younger (34 weeks) hens (P < 0.05). Similarly, labeled enterocytes in distal jejunal sections from poults from the older hens had migrated 28 microns (10%) farther along the crypt-villus axis at hatching, as compared to poults from the younger hens (P < 0.05). Villus growth differences and enterocyte migration were not consistently affected by hen age or egg weight class in poults from 1 to 7 days old. These results suggest that even though intestinal villi may be more advanced developmentally at hatch in poults from the older hens, however post-hatch growth of the intestine or the poult is not affected by hen age or egg weight class.

Influence of beta-adrenergic antagonists on cell proliferation rates in the kidney of untreated and diethylnitrosamine-treated male F344 rats

Some nongenotoxic chemicals which cause kidney tumors have been shown to stimulate tubular cell proliferation. The aim of this study was to evaluate the effects of two beta-adrenoreceptor blocking agents, propranolol and atenolol, on cell proliferation rates in the kidneys of male F344 rats. Immunohistochemical expression of proliferating cell nuclear antigen (PCNA) and mitotic index have been examined in formalin-stored kidneys from F344 rats used in an initiation-promotion study of carcinogenesis. Cell proliferation rate was quantified in the proximal tubule epithelium. Non-initiated rats and rats initiated with a single dose of diethylnitrosamine (DEN, 200 mg/kg, i.p.) were continuously treated with propranolol (75-100 mg/kg) or atenolol (300 mg/kg) by gavage and were sacrificed after 2, 4, 8 or 21 months of experimentation. There were two control groups, one untreated (D1) and one given distilled water by gavage (D1). Control group D1 showed significantly lower cell proliferation rates than the D0 group. In non-initiated rats, propranolol had a weak enhancing effect on cell proliferation, most evident after 4 months, while atenolol had a clear enhancing effect most evident after 8 months of promoting regimen. Treatment with DENalone resulted in a significant increase in cell proliferation rate as compared to group D1. In DEN-initiated rats given propranolol, there was a borderline significant increase in cell proliferation rates, compared to rats given DEN alone, after 8 months of promoting regimen. Atenolol had no effect. Because of the differences in body weight gain and food consumption observed among the various groups, it is suggested that the state of nutrition may have obscured the effects of beta-blockers on cell proliferation rates.

Lysozyme expression during metaplastic squamous differentiation of retinoic acid-deficient human tracheobronchial epithelial cells

We previously reported (Gray, T. E., K. Guzman, C. W. Davis, L. H. Abdullah, and P. Nettesheim. 1996. Mucociliary differentiation of serially passaged normal human tracheobronchial epithelial cells. Am. J. Respir. Cell Mol. Biol. 14:104-112) that retinoic acid (RA)-deprived cultures of normal human tracheobronchial epithelial (NHTBE) cells became squamous, failed to produce mucin, and instead secreted or released large amounts of lysozyme (LZ). The purpose of the studies reported here was to elucidate the relationship between RA deficiency-induced squamous differentiation and increased LZ, and to determine what mechanisms were involved. We found that intracellular LZ began to accumulate in RA-deficient NHTBE cultures early during squamous differentiation. Between Days 10 and 18 of culture, cellular LZ levels were more than 10 times higher in RA-deficient than in RA-sufficient cultures. On Day 12, large numbers of cells began to exfoliate in RA-deficient cultures and extracellular LZ appeared at the apical surface, presumably released from the exfoliated cells. Metabolic labeling studies showed that the rate of LZ synthesis was not increased in RA-deficient cultures over that in RA-sufficient cultures; however, intracellular LZ half-life was much longer in RA-deficient cultures. We concluded that the increased accumulation of both intra- and extracellular LZ in RA-deficient cultures was due to increased LZ stability and was not the result of increased LZ synthesis. When RA-deficient cultures were treated on Day 7 with 10(-6) M RA, intracellular LZ levels did not substantially decrease until 3 d later, coinciding with a marked increase in mucin secretion. LZ messenger RNA levels were unchanged at 24 h, but were modestly increased (rather than decreased) at all subsequent time points. We concluded that RA does not directly regulate LZ, and that the excessive accumulation of LZ in RA-deprived NHTBE cells is a consequence of vitamin A deficiency-induced abnormal differentiation.

Repeat exposure to incremental doses of acetaminophen provides protection against acetaminophen-induced lethality in mice: an explanation for high acetaminophen dosage in humans without hepatic injury

In studies designed to simulate a clinical observation in which an individual became tolerant to normally lethal doses of acetaminophen (APAP), mice were pretreated with increasing doses of APAP for 8 days and challenged on day 9 with normally supralethal doses of APAP. These animals developed minimal hepatotoxicity after a challenge dose with a fourfold increase in LD50 to 1,350 mg/kg. The pretreatment regimen resulted in hepatic changes including: centrilobular localization of 3-(cysteine-S-yl)APAP protein adducts, selective down-regulation of cytochrome P4502E1 (CYP2E1) and CYP1A2 that produced the toxic metabolite, N-acetyl-p-benzoquinone imine, higher levels of reduced glutathione (GSH), centrilobular inflammation, and a fourfold increase in hepatocellular proliferation. The protection against the lethal APAP doses afforded by pretreatment is secondary to these changes and to the associated regional shift in the bioactivation of the APAP challenge dose from centrilobular to periportal regions where CYP2E1 is not found, protective GSH is more abundant, and where cell-proliferative responses are better able to sustain repair. This shift in APAP bioactivation results in less-intense covalent binding that is more diffuse and spread uniformly throughout the hepatic lobe, most likely contributing to protection by delaying the early onset of liver injury that has been generally associated with centrilobular localization of the adducts. Intervention of APAP pretreatment-induced cell division in mice with colchicine left them resistant to a 500-mg/kg (normally lethal) dose of APAP, but unable to survive a 1,000-mg/kg APAP challenge dose. The data demonstrate multiple mechanistic components to the protection afforded by APAP pretreatment. Whereas metabolic and physiological changes not dependent on cell proliferation are adequate to protect against 500 mg/kg APAP, these changes plus a potentiated cell-proliferative response are necessary for protection against the supralethal 1,000-mg/kg APAP dose. Furthermore, the data document an uncoupling of the traditional association between covalent binding and toxicity, and suggest that the assessment of toxicity following repeated or chronic APAP exposure must consider altered drug interactions and parameters besides those historically used to assess acute APAP overdose.

Pimonidazole: a novel hypoxia marker for complementary study of tumor hypoxia and cell proliferation in cervical carcinoma

BACKGROUND

Tumor hypoxia may be associated with treatment resistance, cell proliferation, and metastatic potential, which contribute to poor prognosis. Complementary techniques for detecting hypoxia, cell growth, and metastases are required to study these relationships.

OBJECTIVES

The purpose of this study was to demonstrate the clinical feasibility of quantitative hypoxia detection with pimonidazole, a novel hypoxia marker, and to correlate hypoxia with S-phase markers of tumor proliferation.

METHODS

Pimonidazole binds to thiol-containing proteins specifically in hypoxic cells. Ten patients with cervical carcinoma received 0.5 g/m2 pimonidazole intravenously followed by biopsy of the cervical carcinoma the next day. Hypoxic cells were recognized by immunohistochemical detection of pimonidazole using a mouse monoclonal antibody. Cell proliferation was detected with a commercially available monoclonal antibody for proliferating cell nuclear antigen (PCNA). Assessment of hypoxia and cell proliferation was made qualitatively with light microscopy and quantitatively using point counting and image analysis software methods.

RESULTS

No clinical toxic effects were associated with pimonidazole administration. Immunostaining with pimonidazole antibody was observed in 9 of 10 tumors, suggesting that hypoxia is a common occurrence in cervical carcinoma. Quantitatively, tumors that had large numbers of hypoxic cells had the greatest percentage of S-phase cells, but some tumors with smaller amounts of hypoxia also had substantial numbers of S-phase cells.

CONCLUSION

Pimonidazole can be used for qualitative and quantitative assessment of tumor hypoxia.

Evaluation of sex difference in tissue repair following acute carbon tetrachloride toxicity in male and female Sprague-Dawley rats

Cellular regeneration and tissue repair greatly influence the outcome of acute carbon tetrachloride (CCl4) hepatotoxicity. This study examined the temporal kinetics of cellular regeneration and tissue repair processes in male and female Sprague Dawley (SD) rats following an acute CCl4 exposure (0.8 ml/kg, i.p.). In female rats, hepatic damage peaked at 24 h following the treatment and was approximately 2.5-fold (AST 2.7-fold, ALT 2.3 fold) greater than the damage observed in male rats. The hepatic damage in male rats appeared to peak by 3 h post-exposure and did not significantly change through the 36-h time-point. The activity of cytochrome P 4502E1 was 20% greater in male rats and did not correlate with the magnitude of hepatic damage. Morphometric analysis of cell cycle indices revealed that cellular regeneration was significantly greater in female rats as compared to male rats at 48 h and corresponded proportionally to the extent of liver damage. This study demonstrated that female SD rats respond more severely to acute CCl4 hepatotoxicity than male SD rats and the extent of tissue repair and cellular regeneration was greater in female rats. Furthermore, our results suggest that tissue repair is unlikely to result in accounting for the different responses exhibited by male and female SD rats to CCl4 hepatotoxicity.

Manipulation of metallothionein expression in the regenerating rat liver using antisense oligonucleotides

Metallothioneins (MTs) are low molecular weight, zinc-binding proteins that by activating zinc metalloenzymes participate in the regulation of growth and development. The present study was designed to examine the roles of MTs in cell proliferation using an in vivo model of liver regeneration following partial hepatectomy (PH) in rats. The levels of MT-I and MT-II were studied with respect to regulation of proliferative potential, cell cycle checkpoint activity, and oxidative stress in the rat PH model. We synthesized a 17-mer antisense phosphorothioate oligodeoxynucleotide (S-ODN), named aMT, complimentary to the start site of the MT-I mRNA sequence and an appropriate control. Both S-ODNs were administered intraperitoneally at the dose of 5 mg/kg following 70% PH. MT became induced 57.4 +/- 9.8-fold following PH and the said effect became attenuated dramatically following administration of aMT. In addition, PH rats treated with aMT exhibited decreased rate of liver regeneration as measured by expression of proliferating cell nuclear antigen and elevated cell cycle checkpoint activity as determined by expression of p53. The results of these studies suggest that MT isoforms with their high thiol contents do play an important role in cellular functions and especially during stressful states induced by a broad range of mediators generating free radicals.

Dietary quercetin, immune functions and colonic carcinogenesis in rats

Rats fed 100 mg/kg quercetin (QUE) daily for 7 weeks had significantly enhanced natural killer cell activity compared to their vehicle (VEH)-fed control. In contrast, rats fed 100 mg/kg QUE and treated with the colon carcinogen, azoxymethane had significantly reduced natural killer cell activity compared to their VEH-fed azoxymethane-treated control. There was no significant difference in natural killer cell activity between the two control groups. Antibody production and delayed-type hypersensitivity were not altered by QUE feeding in any treatment group. In vitro exposure of splenic natural killer cells to 1mM QUE significantly decreased natural killer cell cytotoxicity. Lower QUE concentrations produced a non-significant reduction in natural killer cell activity that was restored to control values at 1 x 10(-13)M QUE. The distribution, multiplicity and total number of colonic preneoplastic lesions, aberrant crypt foci, was not significantly different in the QUE-fed azoxymethane-treated rats when compared to azoxymethane-treated vehicle-fed rats at the conclusion of 7 week feeding period. We found no correlation between immune function and development of preneoplastic colon lesions in this study.

1,3,5-Trinitrobenzene-induced alpha-2u-globulin nephropathy

Male and female Fischer-344 (F-344) and male NCI-Black-Reiter (NBR) rats were dosed with 0, 35.5, or 71 mg 1,3,5-trinitrobenzene (TNB)/kg/day for 10 days. Male F-344 rats were dosed with TNB (0 and 35.5 mg/kg) for 20 and 30 days. Hematoxylin and eosin and Mallory-Heidenhain stains and alpha-2u-globulin and proliferating cell nuclear antigen immunohistochemical stains were performed on kidney sections. All treated male F-344 rats exhibited dose-related accumulation of hyaline droplets containing alpha-2u-globulin in proximal tubules. The kidney weights were significantly increased in male and female rats treated with TNB. Significant increases in cell proliferation in proximal tubules were observed in male F-344 rats. Renal changes observed in TNB-treated rats appeared identical to those from other chemicals that induce alpha-2u-globulin nephropathy in male rats. No hyaline droplet accumulation was found in female F-344 and male NBR rats at any doses. We can conclude that TNB induces dose-related exacerbation of hyaline droplets containing alpha-2u-globulin in male rat kidney and subsequent cell proliferation.

Hepatotoxicity in drug development: detection, significance and solutions

Despite considerable progress in the understanding of the mechanism of liver toxicity we are not yet able to design non-hepatotoxic molecules rationally. Also, there is no "universal" in vitro primary screening approach for early identification of hepatotoxic molecules. In most cases hepatotoxicity is detected at later stages of drug development in animal toxicity studies or clinical trials. Although the liver is the most common target organ for drug candidates in animal toxicity studies, hepatotoxicity rarely leads to cessation of drug development during the preclinical phase. Indeed, contrary to other target organs, liver toxicity is usually reversible and can be monitored in man by sensitive serum enzyme tests. Therefore in many cases a compound found hepatotoxic in an animal species will be tested in man for a definitive assessment of its hepatotoxic potential. Liver toxicity in man may be acceptable when a drug has major therapeutic potential. In this situation mechanistic studies are essential to assess the risk in man and in some cases to identify protective agents. When liver toxicity leads to project termination a secondary screening approach may be envisaged if biologically active analogs are available.

Profound effects of the weak environmental estrogen-like chemical bisphenol A on the growth of the mammary gland of Noble rats

In the present study we have examined the effects of the environmental estrogenic chemical bisphenol A on proliferative activity, cell cycle kinetics and differentiation of the mammary gland of female Noble rats. Differentiation measured by the degree of lobular maturation revealed that the conversion of immature structures to mature structures was significantly increased in response to exposure to both low (0.1 mg/kg/day) and high (54 mg/kg/day) doses of bisphenol A compared to controls. The proliferative activity of epithelial cells was increased by 143% over controls by the exposure of animals to the low dose of bisphenol A, whereas a 220% increase over controls was observed for the high dose of bisphenol A. The labelling index and growth fraction were 19% and 27%, respectively, for a low dose of bisphenol A; and 27% and 45%, respectively, for a high dose of bisphenol A, compared to 18% and 31%, respectively, in controls. A significant increase in the conversion of mammary epithelial cells from G0, to G1, and S-phase cells by 1.8 and 4.5-fold, respectively, was observed in animals exposed to the high dose of bisphenol A compared to that of controls. Based on the previously reported estrogenic activity of an equivalent dose of bisphenol A to that of diethylstilbestrol (DES) (0.1 mg/kg/day), a calculated theoretical dose of the order of 10(6)-fold higher of bisphenol A will be required to produce the same biological effects as DES. A comparison of the proliferative activity of DES and that of an equivalent dose of bisphenol A observed in this study, however, revealed that its influence on proliferative activity in the epithelial cells of the mammary gland was profound. The weak estrogenic activity of bisphenol A does not explain its profound effect on cell proliferation observed in this study. Perturbation of the cell cycle is considered a risk factor for the development of cancer. Bisphenol-mediated perturbation of the cell cycle in epithelial cells may produce adverse effects in the mammary glands of Noble rats.

Importance of and approaches to quantification of hepatocyte apoptosis

Abnormal regulation of the life cycle of cells is a key feature of neoplasia. The net increase and growth of initiated cells, preneoplastic lesions, and tumors is highly dependent on rates of both cell proliferation and cell death. Studies of mechanisms involved in regulation of cell death and the development of methods to detect dying and dead cells thus appear to be as important as measurements of cell proliferation in understanding the growth of both normal, preneoplastic and neoplastic lesions. This article describes apoptosis in the mouse liver and its potential role in liver carcinogenesis. Quantitation of hepatocyte apoptosis is a emerging and evolving research area that will require evaluations as thoroughly as those performed with cell proliferation in order to understand all the variables that might influence its occurrence, measurement, and interpretations. Utilizing available data, various methodologies for identifying hepatocyte apoptosis are presented and compared. Aspects important for the quantitation of apoptosis in liver are emphasized. Accurate quantitation of apoptosis, in conjunction with proliferation measurements, is critical for investigations of the mechanisms of chemically induced carcinogenesis and the development of assays for growth alterations and can be applied to biologically based cancer models.

Comparison of acute hepatocellular proliferating cell nuclear antigen labeling indices and growth fractions, p34cdc2 kinases, and serum enzymes in carbon tetrachloride-treated rats

We evaluated various biomarkers associated with cell proliferation immediately following insult with the classic hepatotoxicant carbon tetrachloride (CCl4). Rats were administered a single necrogenic dose of CCl4 and euthanized at either t = 4, 8, 12, 16, or 24 hr postdose. Parameters evaluated included the following: immunohistochemical detection of hepatocellular proliferating cell nuclear antigen labeling indices (PCNA-LIs; percentage of cells in S phase) and growth fractions (PCNA-GFs; percentage of cells in the cell cycle); PCNA and the cyclin-dependent kinase p34cdc2 (CDK) protein in S-9 fractions by Western blot and enzyme-linked immunosorbent assay (ELISA); and liver-related serum enzymes. An increase in PCNA-GF was observed at t = 4 hr, concomitant with elevations in CDK and PCNA protein (Western blot). PCNA-LIs were increased by t = 24 hr, as were CDK and PCNA by ELISA. Sorbitol dehydrogenase was the most sensitive enzyme, with increases observed at t = 4 hr. Our results indicate that PCNA-GF, CDK, and PCNA levels reflect hepatocellular regeneration as early as 4 hr following CCl4 insult. We conclude that these assays are early and sensitive indicators of acute hepatotoxicity that may be advantageous to evaluate in the early stages of exploratory studies.

Xenoestrogens alter mammary gland differentiation and cell proliferation in the rat

We investigated mammary gland differentiation and cell proliferation in rats after acute exposure to xenoestrogens. Pubertal female Sprague-Dawley rats (six/group) were treated for 1 week with diethylstilbestrol (DES), genistein, o,p'-DDT, Aroclor 1221, Aroclor 1254, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), or the vehicle, sesame oil. Animals were killed 18 hr after the last treatment. Analysis of mammary whole-mounts revealed that exposure to DES, genistein, and o,p'-DDT resulted in enhanced gland differentiation and increased epithelial cell proliferation as measured by proliferating cell nuclear antigen immunohistochemistry, TCDD treatment inhibited cell proliferation and gland development. Aroclor 1221 and Aroclor 1254 treatments had slight but not statistically significant effects on cell proliferation and mammary gland development. We conclude that DES, genistein, and o,p'-DDT given to pubertal rats act as morphogens; i.e., they increase cell proliferation, which promotes maturation of the undifferentiated terminal end buds to more differentiated lobular terminal ductal structures.

The potential for the use of cell proliferation and oncogene expression as intermediate markers during liver carcinogenesis

Intense research using animal models has indicated that chemically-induced rat liver cancer proceeds through multiple, distinct stages that can be characterised morphologically and biochemically. Primary human liver cancer, with hepatitis B and other environmental factors such as poor nutrition and food contaminating mycotoxins as contributing etiological factors, is one of the major causes of cancer deaths in African, Asian and some Western countries. Recent advances in surgical and diagnostic techniques have also allowed the identification of potential morphological precursors of primary human liver cancer, and suggested a model consistent with the concepts of initiation--promotion--progression as in the rat. The expression of proliferating cell nuclear antigen (PCNA), silver-staining nucleolar organiser regions (AgNOR), oncogenes and the tumor suppressor gene p53 in preneoplastic and neoplastic lesions of rat and human livers is presently reviewed. This undertaking is an attempt to evaluate whether the current knowledge regarding molecular mechanisms of carcinogenesis is sufficient to permit the use of these molecular parameters as 'intermediate' markers in studies of risk assessment and cancer prevention, without having to resort to tumor appearance as an end-point.