Inflammatory large bowel disease in immunodeficient rats naturally and experimentally infected with Helicobacter bilis

Proliferative and ulcerative typhlitis, colitis, and proctitis were found incidentally in a breeding colony of male athymic nude (Cr:NIH-rnu) rats. Within the crypts of the large intestine, modified Steiner's silver stain revealed spiral organisms that were identified by culture, polymerase chain reaction, and sequencing to be Helicobacter bilis. The large bowel disease was reproduced in H. bilis-free male athymic nude rats that were injected intraperitoneally with a culture of H. bilis from the affected colony. The organism was isolated from the feces and cecum of the experimentally infected rats. H. bilis should be considered a potential pathogen in immunocompromised rats. The infection in immunocompromised rats may serve as an animal model for inflammatory large bowel disease.

Receptor and nonreceptor-mediated organ-specific toxicity of di(2-ethylhexyl)phthalate (DEHP) in peroxisome proliferator-activated receptor alpha-null mice

The peroxisome proliferator-activated receptor alpha (PPAR alpha) is the mediator of the biological effects of peroxisome proliferators through control of gene transcription. To determine if the toxic effects of di(2-ethylhexyl)phthalate (DEHP) are mediated by PPAR alpha, we examined its effect in PPAR alpha-null mice. Male Sv/129 mice, PPAR alpha-null (-/-) or wild-type (+/+) were fed ad libitum either a control diet or one containing 12,000 ppm DEHP for up to 24 wk. Significant body weight loss and high mortality was observed in (+/+) mice fed DEHP. By 16 wk, all DEHP-fed (+/+) mice had died of cystic renal tubular disease. In contrast, the (-/-) mice fed DEHP had no changes in body weight until later in the study nor increased mortality. Histologically, (+/+) mice fed DEHP had typical toxic lesions in liver, kidney, and testis while (-/-) mice fed DEHP had no toxic liver lesions but did show evidence of toxicity in kidney and testis after 4-8 wk of feeding, which progressed into moderate lesions by 24 wk. Analysis of hepatic and renal mRNAs showed a typical pleiotropic response in gene expression in the DEHP-fed (+/+) mice that was absent in the DEHP-fed (-/-) mice. These results provide evidence that PPAR alpha mediates the subacute-chronic toxicity of DEHP in liver, kidney, and testis. However, because (-/-) mice did develop toxic lesions in kidney and testis, DEHP can also act through PPAR alpha-independent pathways in mediating renal and testicular toxicity.

Expression of KAI1 in paraffin-embedded normal, hyperplastic and neoplastic prostate and prostate carcinoma cell lines

Expression of KAI1, a tumor metastasis suppressor gene, was studied with different fixatives in frozen and paraffin-embedded sections of human and rat prostate carcinoma cell lines and human prostate lesions by immunohistochemistry. Immunoreactivity of the membrane antigen in cell lines was associated with known expression levels in these lines and the fixative used. Formalin and paraformaldehyde helped maintain the immunoreactivity of cells. In human prostate, frozen sections revealed diffuse reactivity of the antigen in normal and neoplastic tissues while paraffin-embedded tissues usually showed focal reactivity, although more than 50% of cases with normal epithelium and adenocarcinomas were reactive. In some cases, pretreatment with trypsin enhanced immunoreactivity. Benign prostatic hyperplasia (BPH) showed the most intense diffuse immunoreactivity, which suggested enhanced expression. Prostatic intraepithelial neoplasia (PIN) also often expressed high levels of KAI1. Three of five metastases were reactive but two primaries and their metastases were not. Lymphocytes in primary carcinomas and lymphocytes and germinal center cells in lymph nodes were immunoreactive, while adjacent primary or metastatic prostate adenocarcinoma epithelium was not immunoreactive. Although paraffin-embedded human tissues were not optimal for determining levels of expression of KAI1, they did show immunoreactivity that could have prognostic value and showed the specific cytoplasmic localization of the protein in cells.

Altered expression of transforming growth factor betas during urethral and bulbourethral gland tumor progression in transgenic mice carrying the androgen-responsive C3(1) 5' flanking region fused to SV40 large T antigen

We demonstrate that targeted expression of SV40 large T antigen (TAg) to the urethral (periurethral) and bulbourethral gland epithelium leads to adenocarcinoma formation in these tissues after 7 months of age, which are extremely rare sites for spontaneous tumor formation in humans. The development of proliferative lesions in the urethral gland predictably follows a temporal course of progression with approximately one third of male animals developing urethral tumors by 1 year of age. Tumor progression in these organs correlates to the level of TAg and p53 expression. Immunoprecipitation confirmed that SV40 TAg protein was bound to p53 and Rb p110 in vivo. Expression of transforming growth factor beta (TGFbetas) was evaluated during tumor progression of urethral gland carcinomas. Elevations of intracellular and extracellular TGFbeta1 and extracellular TGFbeta3 were found in preneoplastic and neoplastic lesions, suggesting that increased TGFbetas may augment tumor growth. c-Met expression showed a tendency for increased expression in the urethral gland carcinomas. We speculate that the directed expression of SV40 TAg by the hormone responsive C3(1) gene and subsequent tumor formation in these organs is influenced by androgens, since these tissues and carcinomas express androgen receptor (AR) and arise only in male transgenic mice. Several cell lines established from the urethral carcinomas were also shown to express AR, but are not androgen dependent in culture. To our knowledge, this is the first transgenic animal model for urethral and bulbourethral carcinomas. This transgenic mouse model and the cell lines derived from it may provide a unique opportunity for dissecting molecular mechanisms involved in the tumorigenesis of these organs which otherwise rarely develop cancer.

Sucrose transport in higher plants

Presumably due to its physicochemical properties, sucrose represents the major transport form of photosynthetically assimilated carbohydrates in plants. Sucrose synthesized in green leaves is transported via the phloem, the long distance distribution network for assimilates in order to supply nonphotosynthetic organs with energy and carbon skeletons. At least in Solanaceae, sugar export seems to be a tightly regulated process involving a number of specific plasma membrane proteins. Significant progress in this field was made possible by the recent identification of plasma membrane sucrose transporter genes. These carriers represent important parts of the long-distance transport machinery and can serve as a starting point to obtain a complete picture of long-distance sucrose transport in plants. A combination of biochemical studies of transporter properties together with expression and localization studies allow specific functions to be assigned to the individual proteins. Furthermore, the use of transgenic plants specifically impaired in sucrose transporter expression has provided strong evidence that SUT1 transporter function is required for phloem loading. Physiological analyses of these plants demonstrate that sucrose transporters are essential components of the sucrose translocation pathway at least in potato and tobacco.

Promotion by Helicobacter hepaticus-induced hepatitis of hepatic tumors initiated by N-nitrosodimethylamine in male A/JCr mice

A new murine Helicobacter species, Helicobacter hepaticus, infects the livers of mice, causing a progressive chronic active hepatitis culminating in hepatocellular tumors. To examine the role of chronic H. hepaticus infection in carcinogenesis, H. hepaticus-infected male infant mice of A/JCr strain were given a single i.p. dose of N-nitrosodimethylamine (NDMA). Noninfected A/J mice similarly treated with NDMA served as controls. The effect of hepatitis induced by H. hepaticus was studied for 64 wk. At 31-36 wk, the incidence of hepatocellular adenomas in infected mice was significantly higher than in noninfected mice (82 vs 52%; p = 0.05). The multiplicity of hepatocellular tumors was also significantly higher in infected mice compared to noninfected mice (3.2 +/- 0.09 vs 0.09 +/- 0.2; p = 0.03). At 51-64 wk, many (10/18) infected mice developed hepatocellular carcinomas while only 2 of 19 control mice developed such tumors (p = 0.005). Overexpression of cyclin D was observed in hepatocytes as well as adenomas induced by NDMA in H. hepaticus-infected mice, suggesting its role in inflammation, abnormal cell growth, and early neoplasia. High molecular weight keratins were highly expressed in hyperplastic oval cells in hepatitis and in liver tumors in mice with hepatitis, establishing a reliable marker for oval cells in formalin-fixed, paraffin-embedded tissue. Thus, chronic H. hepaticus infection significantly stimulated cyclin D expression, accelerated the development of liver tumors, increased the multiplicity of such lesions, and enhanced the progression of benign to malignant tumors.

Lesions of aryl-hydrocarbon receptor-deficient mice

We have analyzed the possible role of the aryl-hydrocarbon receptor (AHR) in the aging process of mice using a homozygous null mouse (Ahr-/-) line as a model. We studied 52 male and female Ahr-/- mice aged from 6-13 months. Forty-six percent died or were ill by 13 months of age. Ahr-/- mice developed age-related lesions in several organs, some of which were apparent after only 9 months of age. Cardiovascular alterations included cardiomyopathy (100%) with hypertrophy and focal fibrosis. Vascular hypertrophy and mild fibrosis were found in the portal areas of the liver (81%), and vascular hypertrophy and mineralization were common in the uterus (70%). Gastric hyperplasia that progressed with age into polyps was evident in the pylorus of 71% of the mice over 9 months of age. Ahr-/- mice had T-cell deficiency in their spleens but not in other lymphoid organs. The immune system deficiency described previously could be the origin for the rectal prolapse found in 48% of the null mice, associated with Helicobacter hepaticus infection. In the dorsal skin (53% incidence), severe, localized, interfollicular and follicular epidermal hyperplasia, with hyperkeratosis and acanthosis, and marked dermal fibrosis, associated with the presence of anagenic hair follicles, were also evident. None of these lesions were found in 42 control (Ahr +/+ or +/-) mice of similar ages. These observations suggest that the AHR protein, in the absence of an apparent exogenous (xenobiotic) ligand, plays an important role in physiology and homeostasis in major organs in mice, and further supports an evolutionary conserved role for this transcription factor.

Proliferative lesions of oviduct and uterus in CD-1 mice exposed prenatally to tamoxifen

Tamoxifen (TAM) is widely used as adjuvant breast cancer therapy after surgery and as a chemopreventive agent in women of child-bearing age. However, TAM therapy has been shown to result in an increased incidence of endometrial carcinoma in women. The present study was designed to investigate the effects of TAM (5 mg/kg and 7.5 mg/kg body wt) given i.g. to pregnant CD-1 mice (1x/day, days 12 through 18 of gestation) on their female offspring. Progressive proliferative hyperplasia of the oviduct was frequently seen in TAM-exposed offspring, reaching 100% incidence by 52 weeks in both treatment groups. These females also developed progressive proliferative uterine lesions, including moderate/severe cystic endometrial hyperplasia (34-50%) and polypoid adenomas (27-30%) between 53 and 78 weeks. Deciduomas (15%) occurred at young ages (12 and 24 weeks) while leiomyomas (14%), a malignant leiomyosarcoma, and ovarian granulosa cell tumors (14%), were found between 72 and 78 weeks. Our findings thus suggest a strong association between transplacental TAM and reproductive tract abnormalities in female CD-1 mice.

Making Medicaid child dental services work: a partnership in Washington state

Eighty-one percent of general dentists and 86 percent of pediatric dentists who are members of the local dental society in Spokane County, Washington, participated in a pilot program to provide dental care in private offices to children up to 5 years of age from low-income families served by the Medicaid program. Outreach staff from the local public health agency recruited and enrolled families in the program. University faculty provided special training in the care of young children to the dentists participating in the program. In the program's first year, 37 percent of the enrolled children had made at least one visit to the dentist, in contrast to 12 percent of children who were not enrolled in the program.

Increased oxidative DNA damage and hepatocyte overexpression of specific cytochrome P450 isoforms in hepatitis of mice infected with Helicobacter hepaticus

A recently discovered bacterium, Helicobacter hepaticus, infects the intrahepatic bile canaliculi of mice, causing a severe chronic hepatitis culminating in liver cancer. Thus, it affords an animal model for study of bacteria-associated tumorigenesis including H. pylori-related gastric cancer. Reactive oxygen species are often postulated to contribute to this process. We now report that hepatitis of male mice infected with H. hepaticus show significant increases in the oxidatively damaged DNA deoxynucleoside 8-hydroxydeoxyguanosine, with the degree of damage increasing with progression of the disease. Perfusion of infected livers with nitro blue tetrazolium revealed that superoxide was produced in the cytoplasm of hepatocytes, especially in association with plasmacytic infiltrates near portal triads. Contrary to expectations, Kupffer cells, macrophages, and neutrophils were rarely involved. However, levels of cytochrome P450 (CYP) isoforms 1A2 and 2A5 in hepatocytes appeared to be greatly increased, as indicated by the number of cells positive in immunohistochemistry and the intensity of staining in many cells, concomitant with severe hepatitis. The CYP2A5 immunohistochemical staining co-localized with formazan deposits resulting from nitro blue tetrazolium reduction and occurred in nuclei as well as cytoplasm. These findings suggest that CYP2A5 contributes to the superoxide production and 8-hydroxydeoxyguanosine formation, although reactive oxygen species from an unknown source in the hepatocytes leading to CYP2A5 induction or coincidental occurrence of these events are also possibilities. Three glutathione S-transferase isoforms, mGSTP1-1 (pi), mGSTA1-1 (YaYa), and mGSTA4-4, also showed striking increases evidencing major oxidative stress in these livers.

Osteochondrodysplasia occurring in transgenic mice expressing interferon-gamma

In addition to various biological activities, interferon-gamma (IFN-gamma) inhibits bone resorption and collagen synthesis. We produced a transgenic mouse line expressing the murine IFN-gamma gene and protein in the bone marrow and thymus. Forty-five transgenic FVB/NCr mice, 23 days-9 months of age, were studied for anomalies in the skeletal system. The transgenic mice had short, wide, and deformed long bones. Young transgenic mice had epiphyseal plates severely thickened with zones of hypertrophy and degeneration with irregular metaphyseal borders. Cartilagenous masses were also observed in the metadiaphyseal marrow cavities. These lesions were primarily seen in long bones and ribs. Adult transgenic mice had residues of degenerated cartilagenous masses in the diaphyses. Many osteoclasts with well-developed ruffled borders were present on the metaphyseal cartilagenous masses in young transgenic mice. Adult transgenic mice had less prominent primary spongiosa with fewer osteoclasts at the metaphysis as compared with nontransgenic controls. The cortical bones of the transgenic mice were thinner and more immature compared with controls. Transgenic mice also had fractures, disruption of the epiphyseal plate, and degeneration of articular cartilage. Thus, the IFN-gamma transgenic mice developed a complex chondro-osseous lesion that was diagnosed as osteochondrodysplasia. The lesions may originate from primarily decreased matrix synthesis in bone and cartilage and also possible osteoclast-related changes caused by IFN-gamma overexpression in the bone marrow. Our IFN-gamma transgenic mouse will be a useful model to investigate the role of IFN-gamma in bone metabolism.

Defective placental vasculogenesis causes embryonic lethality in VHL-deficient mice

Inheritance of an inactivated form of the VHL tumor suppressor gene predisposes patients to develop von Hippel-Lindau disease, and somatic VHL inactivation is an early genetic event leading to the development of sporadic renal cell carcinoma. The VHL gene was disrupted by targeted homologous recombination in murine embryonic stem cells, and a mouse line containing an inactivated VHL allele was generated. While heterozygous VHL (+/-) mice appeared phenotypically normal, VHL -/- mice died in utero at 10.5 to 12.5 days of gestation (E10.5 to E12.5). Homozygous VHL -/- embryos appeared to develop normally until E9.5 to E10.5, when placental dysgenesis developed. Embryonic vasculogenesis of the placenta failed to occur in VHL -/- mice, and hemorrhagic lesions developed in the placenta. Subsequent hemorrhage in VHL -/- embryos caused necrosis and death. These results indicate that VHL expression is critical for normal extraembryonic vascular development.

The Staphylococcus aureus ileS gene, encoding isoleucyl-tRNA synthetase, is a member of the T-box family

The Staphylococcus aureus ileS gene, encoding isoleucyl-tRNA synthetase (IleRS), contains a long mRNA leader region. This region exhibits many of the features of the gram-positive synthetase gene family, including the T box and leader region terminator and antiterminator. The terminator was shown to be functional in vivo, and readthrough increased during growth in the presence of mupirocin, an inhibitor of IleRS activity. The S. aureus ileS leader structure includes several critical differences from the other members of the T-box family, suggesting that regulation of this gene in S. aureus may exhibit unique features.

Severe fibronectin-deposit renal glomerular disease in mice lacking uteroglobin

Despite myriads of biological activities ascribed to uteroglobin (UG), a steroid-inducible secreted protein, its physiological functions are unknown. Mice in which the uteroglobin gene was disrupted had severe renal disease that was associated with massive glomerular deposition of predominantly multimeric fibronectin (Fn). The molecular mechanism that normally prevents Fn deposition appears to involve high-affinity binding of UG with Fn to form Fn-UG heteromers that counteract Fn self-aggregation, which is required for abnormal tissue deposition. Thus, UG is essential for maintaining normal renal function in mice, which raises the possibility that an analogous pathogenic mechanism may underlie genetic Fn-deposit human glomerular disease.

Focal segmental glomerulosclerosis in primates infected with a simian immunodeficiency virus

Focal and segmental glomerulosclerosis (FSG) with endothelial tubuloreticular inclusions (TRIs) is the typical lesion of human HIV-associated glomerulopathy. Autopsy studies showed the presence of FSG in 3 of 15 macaques dying 15-120 weeks after experimental infection with a simian immunodeficiency virus (SIVMne). Ultrastructural studies generally revealed numerous endothelial TRIs (also present in normals), mesangial expansion, and evidence of mesangial cell injury. One additional animal had a small-vessel polyarteritis with a proliferative and focally crescentic glomerulonephritis; seven animals had mild, multifocal interstitial nephritis. All animals had documented viremia after infection; 14 of 15 developed antibodies to SIV postinoculation. Additional postmortem findings included severe enterocolitis, encephalitis, and opportunistic infections. In contrast, autopsy studies of macaques infected with a type D simian retrovirus (SAIDS-D/Washington, SRV-2) for similar periods of time (n = 40) showed no evidence of FSG. One SRV-infected animal had a mild proliferative glomerulonephritis. These studies indicate SIV-infected primates may provide a relevant model for study of human HIV-associated nephropathy. They also indicate the variable pathology that can be seen in primate infections of distinct retrovirus types, each of which produces a simian immunodeficiency state that resembles human AIDS.

Enhanced sensitivity to tumor growth and development in multistage skin carcinogenesis by transforming growth factor-alpha-induced epidermal growth factor receptor activation but not p53 inactivation

Transforming growth factor-alpha (TGF alpha) can stimulate keratinocyte proliferation and function as an autocrine tumor promoter in 7,12-dimethylbenz[a]anthracene (DMBA)-initiated TGF alpha-transgenic mouse skin. In this study, we examined the effect of ectopic TGF alpha transgene expression on skin tumor growth and progression after DMBA initiation in the presence of 12-O-tetradecanoylphorbol-13-acetate (TPA). Both the multiplicity and size of skin tumors arising in TGF alpha-transgenic mice were significantly higher than those of the nontransgenic parental CD-1 strain. There were more dysplastic papillomas and squamous cell carcinomas (SCCs) in the transgenic animals as well. ProTGF alpha protein was expressed in transgenic papillomas, but mature TGF alpha was not detected. The epidermal growth factor receptor (EGFR) appeared to be downregulated and was associated with enhanced tyrosine phosphorylation of several substrates in TGF alpha-transgenic mouse tumors. Characteristic codon 61 mutations in the Ha-ras gene were found in most of the papillomas and SCCs induced by DMBA and TPA in transgenic as well as nontransgenic mice. However, no p53 gene mutations were found in any skin tumors from either transgenic or control animals. Analysis of cellular proliferation in both DMBA-TPA-induced papillomas and in skin 48 h after TPA treatment alone revealed significantly more DNA synthesis in TGF alpha-transgenic mice relative to controls. These results demonstrate that TGF alpha, through EGFR overstimulation, can act synergistically with TPA to induce the formation, growth, and development of DMBA-initiated skin tumors containing classic Ha-ras gene mutations but not p53 gene inactivation.

Differential abscisic acid regulation of guard cell slow anion channels in Arabidopsis wild-type and abi1 and abi2 mutants

Abscisic acid (ABA) regulates vital physiological responses, and a number of events in the ABA signaling cascade remain to be identified. To allow quantitative analysis of genetic signaling mutants, patch-clamp experiments were developed and performed with the previously inaccessible Arabidopsis guard cells from the wild type and ABA-insensitive (abi) mutants. Slow anion channels have been proposed to play a rate-limiting role in ABA-induced stomatal closing. We now directly demonstrate that ABA strongly activates slow anion channels in wild-type guard cells. Furthermore, ABA-induced anion channel activation and stomatal closing were suppressed by protein phosphatase inhibitors. In abi1-1 and abi2-1 mutant guard cells, ABA activation of slow anion channels and ABA-induced stomatal closing were abolished. These impairments in ABA signaling were partially rescued by kinase inhibitors in abi1 but not in abi2 guard cells. These data provide cell biological evidence that the abi2 locus disrupts early ABA signaling, that abi1 and abi2 affect ABA signaling at different steps in the cascade, and that protein kinases act as negative regulators of ABA signaling in Arabidopsis. New models for ABA signaling pathways and roles for abi1, abi2, and protein kinases and phosphatases are discussed.

Bone marrow and thymus expression of interferon-gamma results in severe B-cell lineage reduction, T-cell lineage alterations, and hematopoietic progenitor deficiencies

Interferon-gamma (IFN-gamma) is an immunoregulatory lymphokine that is primarily produced by T cells and natural killer cells. It has effects on T-cell, B-cell, and macrophage differentiation and maturation. We have developed transgenic mice that express elevated levels of IFN-gamma mRNA and protein by inserting multiple copies of murine IFN-gamma genomic DNA containing an Ig lambda-chain enhancer in the first intron. The founder line carrying eight copies of this transgene has eightfold to 15-fold more IFN-gamma-producing cells in the bone marrow and spleen than do nontransgenic littermates. Transgenic mice show a pronounced reduction in B-lineage cells in the bone marrow, spleen, and lymph nodes. In addition, single positive (CD4+,CD8- and CD4-,CD8+) thymocyte numbers are increased twofold, yet the number of splenic T cells is reduced by 50%. There is also a twofold to threefold decrease in the frequency and total number of myeloid progenitors in the bone marrow. Granulomatous lesions and residual degenerating cartilaginous masses are also present in the bones of these mice. Overall, our data show that the abnormal expression of IFN-gamma in these transgenic mice results in multiple alterations in the immune system. These animals provide an important model to examine the role of IFN-gamma expression on lymphoid and myeloid differentiation and function.

A novel chloride channel in Vicia faba guard cell vacuoles activated by the serine/threonine kinase, CDPK

Calcium-Dependent Protein Kinases (CDPKs) in higher plants contain a C-terminal calmodulin-like regulatory domain. Little is known regarding physiological CDPK targets. Both kinase activity and multiple Ca2+-dependent signaling pathways have been implicated in the control of stomatal guard cell movements. To determine whether CDPK or other protein kinases could have a role in guard cell signaling, purified and recombinant kinases were applied to Vicia faba guard cell vacuoles during patch-clamp experiments. CDPK activated novel vacuolar chloride (VCL) and malate conductances in guard cells. Activation was dependent on both Ca2+ and ATP. Furthermore, VCL activation occurred in the absence of Ca2+ using a Ca2+-independent, constitutively active, CDPK* mutant. Protein kinase A showed weaker activation (22% as compared with CDPK). Current reversals in whole vacuole recordings shifted with the Nernst potential for Cl-and vanished in glutamate. Single channel recordings showed a CDPK-activated 34 +/- 5 pS Cl- channel. VCL channels were activated at physiological potentials enabling Cl- uptake into vacuoles. VCL channels may provide a previously unidentified, but necessary, pathway for anion uptake into vacuoles required for stomatal opening. CDPK-activated VCL currents were also observed in red beet vacuoles suggesting that these channels may provide a more general mechanism for kinase-dependent anion uptake.

The semidominant Mi(b) mutation identifies a role for the HLH domain in DNA binding in addition to its role in protein dimerization

The mouse microphthalmia (mi) locus encodes a basic helix-loop-helix-leucine zipper (bHLH-Zip) transcription factor called MITF (microphthalmia transcription factor). Mutations at mi affect the development of several different cell types, including melanocytes, mast cells, osteoclasts and pigmented epithelial cells of the eye. Here we describe the phenotypic and molecular characterization of the semidominant Microphthalmia(brwnish) (Mi(b)) mutation. We show that this mutation primarily affects melanocytes and produces retinal degeneration. The mutation is a G to A transition leading to a Gly244Glu substitution in helix 2 of the HLH dimerization domain. This location is surprising since other semidominant mi mutations characterized to date have been shown to affect DNA binding or transcriptional activation domains of MITF and act as dominant negatives, while mutations that affect MITF dimerization are inherited recessively. Gel retardation assays showed that while the mutant MITF(Mi-b) protein retains its dimerization potential, it is defective in its ability to bind DNA. Computer modeling suggested that the Gly244Glu mutation might disrupt DNA binding by interfering with productive docking of the protein dimer onto DNA. The Mi(b) mutation therefore appears to dissociate a DNA recognition function of the HLH domain from its role in protein dimerization.

Progression of prostatic intraepithelial neoplasia to invasive carcinoma in C3(1)/SV40 large T antigen transgenic mice: histopathological and molecular biological alterations

The progression of prostatic intraepithelial neoplasia (PIN) to invasive prostate carcinoma has been analyzed in the C3(1)/T(AG) transgenic mouse model and appears very similar to the process proposed to occur in humans. PIN lesions in these transgenic mice histologically resemble those found in human PIN. Low-grade PIN was observed in the ventral and dorsolateral lobes at 2 months of age, whereas high-grade PIN was found in both lobes by 5 months of age. A progressive increase in the number of PIN lesions was observed with age. Prostate carcinomas, which appeared to arise from PIN lesions, were found by 7 months of age in the ventral lobe and 11 months of age in the dorsolateral lobe. Expression of T(AG) mRNA and protein in these lesions correlated with the development of PIN and carcinomas, as did the overexpression of p53 protein. Apoptosis levels were quite low in normal epithelial cells, moderate in low-grade PIN, and high in high-grade PIN and carcinomas. Levels of expression of proliferating cell nuclear antigen correlated with the degree of severity of the prostate lesions. Eighteen % of PIN lesions were found to already harbor Ha-ras mutations, whereas 33% of carcinomas showed various mutations in Ha-ras, Ki-ras, and/or p53. Mutations in Ha-ras may, therefore, be an early event in a significant portion of PIN lesions. Because high-grade PIN showed many characteristics similar to those observed in carcinomas and high-grade PIN was often found contiguous to carcinomas, we conclude that high-grade PIN is a precursor lesion of prostate carcinoma in this transgenic model. These transgenic mice will be useful to study mechanisms responsible for the progression of invasive carcinomas from PIN precursor lesions, as may occur during the development of prostate cancer in humans.

Organic acid excretion by Streptomyces lividans TK24 during growth on defined carbon and nitrogen sources

Cultures of Streptomyces lividans TK24 grown in defined media containing certain rapidly used carbon and nitrogen sources excreted high levels of organic acids. These were identified by HPLC and enzymic assays as pyruvic acid and 2-oxoglutaric acid. Acidification occurred only with glucose as the principal carbon source, and depended on the nitrogen source used. With nitrate as the sole nitrogen source, high levels of pyruvate and small amounts of 2-oxoglutarate were produced. Carbon from D[U-14C]glucose was converted into both organic acids. Combining glucose with a selection of amino acids as primary nitrogen/secondary carbon sources yielded less pyruvate and more 2-oxoglutarate. Carbon from both 14C-labelled glucose and amino acids was metabolized to both organic acids. Adding nitrate to this combination caused a reversion of the acid production pattern to that of the glucose-nitrate combination, as if the amino acids were absent. Addition of ammonium salts to any combination of carbon and nitrogen sources completely prevented organic acid formation.