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Biomedical subjects

J M Ward

Publications and source records attributed to J M Ward.

At least 127 records · Page 7Linked to original sources
PubMed1996

Down-regulation of metallothionein expression in human and murine hepatocellular tumors: association with the tumor-necrotizing and antineoplastic effects of cadmium in mice.

Previously, we found that oral cadmium (Cd) treatment either prevented or substantially reduced N-nitrosodiethylamine (NDEA)-induced tumor formation in B6C3F1 mouse liver or lung regardless of exposure interval and even when the Cd was given well after tumors were formed. Because Cd salts are powerful emetics, oral exposure would probably be impractical in humans. Thus, we studied suppression of NDEA-initiated tumors in male B6C3F1 mice by a single i.v. dose of Cd. NDEA (776 mumol/kg i.p.) was given at time 0 followed by CdCl2 (16 mumol/kg i.v.) 40 weeks later. This dose of Cd had no effect on body weights through the conclusion of the study at 52 weeks. The NDEA-induced increase in hepatic tumor incidence (19 tumor-bearing mice/22 mice at risk, 86%) over control (5/24, 21%) was remarkably reduced by Cd treatment (13/27, 48%, P < or = .05). Multiplicity and size of liver tumors induced by NDEA (2.18 tumors/liver; 31.6 mm3 mean volume) were also substantially reduced by the Cd exposure (0.96 tumors/liver; 17.1 mm3 mean volume). NDEA-induced lung tumor incidence (22/22, 100%) and multiplicity (5.09 tumors/lung) were modestly, but significantly, reduced by Cd treatment (21/27, 78%; 3.89 tumors/lung). Clear evidence of tumor-specific cytotoxicity was observed as Cd treatment induced a necrotizing effect that was localized only within the hepatic tumors. Metallothionein (MT), an inducible metal-binding protein associated with tolerance to many metal including Cd, was not detected immunohistochemically in mouse liver tumors, even those undergoing Cd-induced necrosis, whereas the surrounding normal liver cells expressed high levels of MT after Cd exposure. Likewise, in human hepatocellular carcinomas MT was only poorly or erratically expressed relative to normal tissue. These results indicate that a single, nontoxic dose of Cd dramatically reduces liver tumor burden through tumor cell-specific necrosis due to a down-regulation of MT expression in hepatic tumors of murine origin and furthermore indicate that a similar down-regulation of MT occurs in human hepatocellular carcinomas.

Animals↗
PubMed1996

Inflammatory large bowel disease in immunodeficient mice naturally infected with Helicobacter hepaticus.

Large bowel disease detected clinically by rectal prolapse was studied in 64 immunodeficient mice (37 athymic NCr-nu/nu, 12 BALB/c AnNCr-nu/nu, 9 C57BL/6NCr-nu/nu, and 6 C.B17/Icr-scid/NCr) naturally infected with Helicobacter hepaticus. Rectal prolapse was found in approximately 5% of immunodeficient mice maintained in a research facility over a period of 3.5 years. All mice had various degrees of chronic proliferative typhlitis, colitis, and proctitis, usually without concomitant hepatitis. Some mice had severe proliferative proctitis with cystic hyperplasia. Histologic study of the large bowel of 48 athymic NCr-nu/nu mice without H. hepaticus infection and housed in another clean facility revealed only 12% of the mice with minimal-to-mild large bowel inflammation. Helicobacter hepaticus infection is associated with large bowel disease in immunodeficient mice but is not seen in H. hepaticus-infected immunocompetent mice. This new pathogenic bacterial infection should be considered as another potential cause or co-factor for rectal prolapse and large bowel disease in mice.

Animals↗
PubMed1995

Renal tubular tumors and atypical hyperplasias in B6C3F1 mice exposed to lead acetate during gestation and lactation occur with minimal chronic nephropathy.

Lead is a high-priority hazardous substance in humans and a renal carcinogen in adult rodents. This study assessed the carcinogenic potential and toxicity of gestational and lactational lead exposure in (C57BL/6NCr x C3H/HeN)F1 (hereafter called B6C3F1) mice. Effects of a renal tumor promoter [barbital sodium (BB)] on lead-initiated lesions were also studied. Pregnant female C57BL/6NCr mice (10-15/group) previously bred with C3H/HeN males were given lead acetate (0, 500, 750 and 1000 ppm lead) ad libitum in their drinking water, starting on gestation day 12 and continuing to 4 weeks postpartum. Offspring were then weaned and divided into same-sex groups of 23-25 and observed for a maximum of 112 weeks. Other groups received lead and then continuous BB (500 ppm) ad libitum in their drinking water from weaning onward. In control male offspring (0 lead/0 BB), renal proliferative lesions [(RPLs); defined as atypical tubular hyperplasia or tumor] occurred rarely (1 lesion-bearing mouse/23 mice examined, 4%) and did not include tumors. RPLs increased in a dose-related fashion with lead exposure (500 lead/0 BB, 4/25, 16%; 750 lead/0 BB, 6/25, 24%; 1000 lead/0 BB, 12/25, 48%) in male offspring and were often multiple. All lead-treated groups had renal tumors, including carcinoma, but these were most common at the highest dose (1000 lead/0 BB, 5/25). Lead-induced renal tumors arose in the absence of the extensive chronic nephropathy and lead inclusion bodies typically seen with lead carcinogenesis in rodents exposed chronically as adults. Postnatal BB exposure had no effect on RPL incidence (e.g., 1000 lead/500 BB, 8/25, 32%). Lead-treated female offspring also developed RPLs, including adenoma and carcinoma, but at a much lower rate than males. Thus, short-term lead exposure during the gestational/lactational period has carcinogenic potential in the mouse kidney.

Animals↗
PubMed1995

Chemoprevention of spontaneous tumorigenesis in p53-knockout mice.

Spontaneous tumorigenesis was evaluated in male p53-knockout (p53-/-) mice treated with dehydroepiandrosterone (DHEA), quercetin, d-limonene, or all-trans retinoic acid to determine whether tumor development in these mice can be modulated by cancer-chemopreventive agents. DHEA-treated mice experienced a delay in tumorigenesis (particularly lymphomas) and subsequent mortality (P < 0.01) relative to untreated control mice. Quercetin, d-limonene, and all-trans retinoic acid each had no effect on spontaneous tumor development in p53-/- mice. These data demonstrate that tumor development in p53-/- mice can be delayed by DHEA and suggest that p53-/- mice provide a useful model for evaluating strategies to offset the increased risk of tumorigenesis resulting from loss of p53 tumor suppressor function.

Animals↗
PubMed1995

Transfer of the human glucocerebrosidase gene into hematopoietic stem cells of nonablated recipients: successful engraftment and long-term expression of the transgene.

In trying to develop methods of gene therapy for Gaucher disease that will avoid the morbidity and mortality associated with bone marrow (BM) ablation, we transplanted BM stem cells transduced with a retroviral vector containing the human glucocerebrosidase cDNA into normal, nonablated, syngeneic mice. Donor BM from untreated male mice or treated with 5-fluorouracil (5-FU) was transduced ex vivo using a standard 4-day transduction protocol. Recipient female mice were injected one time only or once daily for 5 consecutive days or once a week for 5 consecutive weeks using 2 x 10(7) (untreated BM) or 2 x 10(6) (5-FU-treated BM) cells per injection. Initial transduction efficiency into colony-forming unit-spleen (CFU-S) was 80% to 100%. Recipient analysis was performed at least 6 months after the last transplantation. The best engraftment of donor stem cells, up to 5% by secondary CFU-S analysis, was obtained with multiple injections of transduced BM not previously treated with 5-FU. Polymerase chain reaction (PCR) amplification for both the transgene and the Y chromosome identified the progeny of transduced stem cells in various hematopoietic and non-hematopoietic organs. The copy number of the transgene in stem cells was 0.13 to 2.8. Transgene expression was shown by reverse transcriptase-PCR, in situ hybridization, and immunohistochemistry. No serious side effects of the procedure were noted. We conclude that multiple transplants of retrovirally transduced BM cells into nonablated recipients may be a safe and effective therapeutic modality for a number of genetic hematopoietic disorders.

Animals↗
PubMed1995

Neonatal lethality associated with respiratory distress in mice lacking cytochrome P450 1A2.

Cytochrome P450 1A2 (CYP1A2) is a constitutively expressed hepatic enzyme that is highly conserved among mammals. This protein is primarily involved in oxidative metabolism of xenobiotics and is capable of metabolically activating numerous procarcinogens including aflatoxin B1, arylamines, heterocyclic amine food mutagens, and polycylic aromatic hydrocarbons. Expression of CYP1A2 is induced after exposure to certain aromatic hydrocarbons (i.e., 2,3,7,8-tetrachlorodibenzo-p-dioxin). Direct evidence for a role of CYP1A2 in any physiological or developmental pathway has not been documented. We now demonstrate that mice homozygous for a targeted mutation in the Cyp1a-2 gene are nonviable. Lethality occurs shortly after birth with symptoms of severe respiratory distress. Mutant neonates display impaired respiratory function associated with histological signs of lung immaturity, lack of air in alveoli at birth, and changes in expression of surfactant apoprotein in alveolar type II cells. The penetrance of the phenotype is not complete (19 mutants survived to adulthood out of 599 mice). Surviving animals, although lacking expression of CYP1A2, appear to be normal and are able to reproduce. These findings establish that CYP1A2 is critical for neonatal survival by influencing the physiology of respiration in neonates, thus offering etiological insights for neonatal respiratory distress syndrome.

Animals↗
PubMed1995

Immune system impairment and hepatic fibrosis in mice lacking the dioxin-binding Ah receptor.

The aryl hydrocarbon (Ah) receptor (AHR) mediates many carcinogenic and teratogenic effects of environmentally toxic chemicals such as dioxin. An AHR-deficient (Ahr-/-) mouse line was constructed by homologous recombination in embryonic stem cells. Almost half of the mice died shortly after birth, whereas survivors reached maturity and were fertile. The Ahr-/- mice showed decreased accumulation of lymphocytes in the spleen and lymph nodes, but not in the thymus. The livers of Ahr-/- mice were reduced in size by 50 percent and showed bile duct fibrosis Ahr-/- mice were also nonresponsive with regard to dioxin-mediated induction of genes encoding enzymes that catalyze the metabolism of foreign compounds. Thus, the AHR plays an important role in the development of the liver and the immune system.

Animals↗
PubMed1995

Transplacental carcinogenesis by cisplatin in F344/NCr rats: promotion of kidney tumors by postnatal administration of sodium barbital.

Transplacental carcinogenic effects of cis-dichlorodiammineplatinum (cis-DDP) in F344 rats were investigated. Pregnant F344 rats were given a single i.p. administration of either cis-DDP (5 mg/kg body wt; group 1) or saline only (group 2) on Day 18 of gestation. Offspring of groups 1 and 2 were randomly and equally divided into two subgroups: 1a, 1b and 2a, 2b, respectively. Beginning at 4 weeks of age, offspring in groups 1b and 2b received 500 ppm of sodium barbital (NaBB) in diet, while those in groups 1a and 2a received normal diet. The experiment was terminated at 79 weeks of age. A low incidence (2/19; 10.5%) of male offspring exposed to transplacental cis-DDP (group 1a) developed renal cell adenomas. Postnatal administration of NaBB significantly enhanced this incidence (10/22; p < 0.01) in cis-DDP-initiated offspring. Also, multiple kidney tumors were more common in group 1b than any other group and three animals in this group developed frank renal cell carcinomas. cis-DDP, administered transplacentally, was a complete carcinogen for rat liver as the incidence of hepatocellular adenomas was significantly higher in offspring exposed transplacentally to cis-DDP than in those exposed to saline (20/82 vs 3/75; p < 0.05). NaBB, a known promoter of hepatocellular carcinogenesis in adult rats initiated with N-nitrosodiethylamine, failed to promote liver carcinogenesis initiated by transplacental cis-DDP. Tumors of the central nervous system (3/82; gliomas) and peripheral nervous system (2/82; schwannomas) were found only in offspring exposed transplacentally to cis-DDP. Thus, cis-DDP, administered transplacentally, was a strong initiator of renal cell tumors and a complete carcinogen for multiple organs in rat offspring.

Animals↗
PubMed1995

Immunohistochemical localization of transforming growth factor-beta 1 in Kaposi's sarcoma.

Immunohistochemical localization of transforming growth factor beta 1 (TGF-beta 1) was studied in Kaposi's sarcoma (KS) tissues obtained from autopsy and biopsy materials of patients with and without acquired immunodeficiency syndrome (AIDS) or human immunodeficiency virus (HIV) infection. There was no difference in the localization and distribution of TGF-beta 1 in KS tissues regardless of the HIV-1 status of the patients. Rabbit polyclonal antibodies to synthetic peptides, corresponding to the first 30 amino acids of mature TGF-beta 1, anti-LC(1-30), and anti-CC(1-30), were used for localization of intracellular and extracellular TGF-beta 1. An antibody to a peptide corresponding to amino acids 266 to 278 of the TGF-beta 1 precursor sequence anti-Pre(266 to 278) was used to detect the TGF-beta 1 precursor and the latency-associated peptide. Intracellular mature TGF-beta 1 was demonstrated in mononuclear cells, presumably macrophages, within KS tumors but not in spindle-shaped KS cells. Extracellular mature TGF-beta 1 was localized in the basement membranes of blood vessels and fibrous capsules of KS tumors. Intracellular reactivity to anti-Pre was localized in vascular smooth muscle cells and pericytes within the tumor, in variable proportions of spindle-shaped KS cells, and also in macrophage-like cells. These cells appear to be the production sites of TGF-beta 1, which may exert paracrine as well as autocrine proliferative effects.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Xenobiotic receptor knockout mice.

Administration of certain foreign chemicals to animals elicits responses that are due to receptor-mediated activation of gene expression. Among the most well studied receptors are the Ah receptor (AHR) that binds 2,3,7,8-tetrachlorodibenzo-p-dioxin and related compounds and the peroxisome proliferator-activated receptors, PPARs, that mediate gene activation by the diverse group of peroxisome proliferators. These receptors may also have critical roles in development or physiological homeostasis in addition to their abilities to allow animals to interact with exogenous chemicals or xenobiotics. To explore the function of AHR and PPAR alpha and to determine whether they participate in the adverse effects of dioxins and peroxisome proliferators, gene knockout mice were developed.

Animals↗
PubMed1995

Characterization of transgenic mice with an increased content of chromosomal protein HMG-14 in their chromatin.

Chromosomal protein HMG-14 is a ubiquitous nuclear protein that may modulate the chromatin structure of transcriptionally active genes. To gain insights into the cellular function of the HMG-14 protein, we generated two transgenic mouse lines carrying either two or six copies of the human HMG-14 gene. The transgenic mice express human HMG-14 mRNA and protein in all tissues examined at a level reflecting the increased gene dosage, suggesting that the HMG14 transgene contains all the control regions necessary for regulated gene expression. Expression of the human HMG-14 protein does not alter the expression of the endogenous mouse HMG-14 protein or its close homolog, protein HMG-17. The intracellular distribution of the exogenous human protein is indistinguishable from that of the endogenous mouse protein, resulting in a three-fold increase in the level of the chromatin-bound HMG-14. The transgenic mice had a higher incidence of epithelial cysts in their thymus than did control animals. We conclude that the cellular levels of HMG-14/-17 are determined by gene copy number, that the DNA fragment containing the gene and about 1,000 bp flanking its 5' and 3' ends contain most of the elements necessary for gene expression, that the upper limits of HMG-14 in chromatin are not stringently regulated, and that a three-fold increase in chromatin-bound protein cause only mild phenotypic changes in the transgenic mice.

Animals↗
PubMed1995

A bispecific antibody prolongs survival in mice bearing lung metastases of syngeneic mammary adenocarcinoma.

In the present study we tested whether T cells retargeted with a bispecific antibody (bsAb) could block the growth of lung metastases of syngeneic mammary adenocarcinoma in immunocompetent mice. BALB/c mice were injected i.v. with tumor and i.p. with a genetically engineered bispecific F(ab')2 [bs(Fab')2] having specificity for murine CD3 epsilon chain and for the gp52 mouse mammary tumor viral glycoprotein, which is expressed on the tumor cells. The bs(Fab')2 was physically stable in blood and serum, was removed from the body with a half-time of 12-15 h, and accumulated in lymphoid tissue where it bound to T cells. We show that treatment of tumor bearing mice with the bs(Fab')2 significantly prolonged their survival relative to untreated controls. Two other genetically engineered bs(Fab')2s having specificity for murine CD3 epsilon chain and irrelevant antigens did not inhibit tumor growth. In addition, survival was not affected by bsAb therapy using a variant tumor cell line that expressed low levels of the gp52 target antigen. Inhibition of tumor growth was even more evident by histologic analysis. Treatment with the relevant bs(Fab')2 resulted in a marked reduction of tumor burden in lung sections taken on days 7, 9 and 11. This is the first report demonstrating that a bsAb can inhibit the growth of syngeneic solid tumor metastases in mice without addition of T cell activators.

Adenocarcinoma↗
PubMed1995

Multiple genes, tissue specificity, and expression-dependent modulationcontribute to the functional diversity of potassium channels in Arabidopsis thaliana.

K+ channels play diverse roles in mediating K+ transport and in modulating the membrane potential in higher plant cells during growth and development. Some of the diversity in K+ channel functions may arise from the regulated expression of multiple genes encoding different K+ channel polypeptides. Here we report the isolation of a novel Arabidopsis thaliana cDNA (AKT2) that is highly homologous to the two previously identified K+ channel genes, KAT1 and AKT1. This cDNA mapped to the center of chromosome 4 by restriction fragment length polymorphism analysis and was highly expressed in leaves, whereas AKT1 was mainly expressed in roots. In addition, we show that diversity in K+ channel function may be attributable to differences in expression levels. Increasing KAT1 expression in Xenopus oocytes by polyadenylation of the KAT1 mRNA increased the current amplitude and led to higher levels of KAT1 protein, as assayed in western blots. The increase in KAT1 expression in oocytes produced shifts in the threshold potential for activation to more positive membrane potentials and decreased half-activation times. These results suggest that different levels of expression and tissue-specific expression of different K+ channel isoforms can contribute to the functional diversity of plant K+ channels. The identification of a highly expressed, leaf-specific K+ channel homolog in plants should allow further molecular characterization of K+ channel functions for physiological K+ transport processes in leaves.

Amino Acid Sequence↗
PubMed1995

Increased susceptibility to N-nitrosomethylurea gastric carcinogenesis in transforming growth factor alpha transgenic mice with gastric hyperplasia.

Glandular stomach carcinogenesis after N-nitrosomethylurea (NMU) treatment was examined in transgenic mice bearing a human transforming growth factor alpha (TGF-alpha) cDNA driven by the mouse metallothionein-I promoter (mouse line MT100) in the inbred mouse line FVB/N. Untreated MT100 mice exhibit a severe age-related gastric fundic hyperplasia. Both sexes of MT100 mice were given 10 weekly intragastric intubations of 0.5 mg NMU per mouse from 6 weeks of age and/or zinc chloride in drinking water to stimulate transgene expression from 5.5 weeks of age to the experiment termination. Animals were killed sequentially at 10, 19 and 29 experimental weeks. Several histochemical markers (AB-PAS, TGF-alpha, pepsinogen isozyme 1, proliferating cell nuclear antigen) were used. Abnormal histochemical patterns were found in untreated MT100 and NMU-treated MT100 mice for all 4 markers of differentiation and carcinogenesis. Precancerous lesions including atypical and/or adenomatous hyperplasia were found in the fundic region of 16/22 male and 8/22 female MT100 mice but not in 27 male and 24 female FVB/N mice treated with NMU. One of 22 MT100 males had fundic carcinoma. FVB/N mice treated with NMU had neither precancerous lesions nor carcinomas in the fundus. Well differentiated adenocarcinomas in the pyloric region were induced at incidences of 2/22 male and 1/22 female MT100 mice treated with NMU and 4/27 male and 4/24 female FVB/N mice treated with NMU. Both strains also had a high incidence (55 to 92%) of squamous cell carcinomas of the forestomach. In conclusion, TGF-alpha induced a hyperplastic lesion in the gastric fundus that appeared to predispose the MT100 mice to carcinogenesis by NMU.

Adenocarcinoma↗
PubMed1995

Neuromuscular blocking profile of the vecuronium analogue, Org-9487, in the rat isolated hemidiaphragm preparation.

1. The neuromuscular effects of the short-acting aminosteroid muscle relaxant Org-9487 have been studied in the in vitro rat phrenic nerve/hemidiaphragm preparation by use of twitch tension and electrophysiological recording techniques. 2. Org-9487 (5-100 microM) produced a concentration-dependent decrease in the amplitude of twitches (0.1 Hz) and tetanic contractions (50 Hz) evoked by motor nerve stimulation. The compound produced fade of force during both 50 Hz stimulation and train-of-four stimulation at 2 Hz, indicating a prejunctional component of action. 3. Anticholinesterases only partially reversed the effect of Org-9487 on twitch responses. This was possibly because, at the concentrations required to block twitches in the rat, Org-9487 itself was found to possess significant anticholinesterase activity. 4. Org-9487 (3 microM) increased the rundown of endplate current amplitudes during a 2 s train of 50 Hz nerve stimulation. This was because Org-9487 increased the quantal content of the first endplate current in the train without affecting acetylcholine release towards the latter part of the train. 5. Org-9487 (10 microM) produced a voltage-dependent decrease in the time constant of decay of endplate currents at 32 degrees C and 0.5 Hz, indicative of a block of endplate ion channels. The blocking rate constant increased with membrane hyperpolarization.

Acetylcholine↗
PubMed1995

Effects of a minor isoleucyl tRNA on heterologous protein translation in Escherichia coli.

In Escherichia coli, the isoleucine codon AUA occurs at a frequency of about 0.4% and is the fifth rarest codon in E. coli mRNA. Since there is a correlation between the frequency of codon usage and the level of its cognate tRNA, translational problems might be expected when the mRNA contains high levels of AUA codons. When a hemagglutinin from the influenza virus, a 304-amino-acid protein with 12 (3.9%) AUA codons and 1 tandem codon, and a mupirocin-resistant isoleucyl tRNA synthetase, a 1,024-amino-acid protein, with 33 (3.2%) AUA codons and 2 tandem codons, were expressed in E. coli, product accumulation was highly variable and dependent to some degree on the growth medium. In rich medium, the flu antigen represented about 16% of total cell protein, whereas in minimal medium, it was only 2 to 3% of total cell protein. In the presence of the cloned ileX, which encodes the cognate tRNA for AUA, however, the antigen was 25 to 30% of total cell protein in cells grown in minimal medium. Alternatively, the isoleucyl tRNA synthetase did not accumulate to detectable levels in cells grown in Luria broth unless the ileX tRNA was coexpressed when it accounted for 7 to 9% of total cell protein. These results indicate that the rare isoleucine AUA codon, like the rare arginine codons AGG and AGA, can interfere with the efficient expression of cloned proteins.

Bacterial Proteins↗