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Biomedical subjects

J M Ward

Publications and source records attributed to J M Ward.

At least 199 records · Page 11Linked to original sources
PubMed1992

Proton Transport Activity of the Purified Vacuolar H-ATPase from Oats : Direct Stimulation by Cl.

To determine whether the detergent-solubilized and purified vacuolar H(+)-ATPase from plants was active in H(+) transport, we reconstituted the purified vacuolar ATPase from oat roots (Avena sativa var Lang). Triton-solubilized ATPase activity was purified by gel filtration and ion exchange chromatography. Incorporation of the vacuolar ATPase into liposomes formed from Escherichia coli phospholipids was accomplished by removing Triton X-100 with SM-2 Bio-beads. ATP hydrolysis activity of the reconstituted ATPase was stimulated twofold by gramicidin, suggesting that the enzyme was incorporated into sealed proteoliposomes. Acidification of K(+)-loaded proteoliposomes, monitored by the quenching of acridine orange fluorescence, was stimulated by valinomycin. Because the presence of K(+) and valinomycin dissipates a transmembrane electrical potential, the results indicate that ATP-dependent H(+) pumping was electrogenic. Both H(+) pumping and ATP hydrolysis activity of reconstituted preparations were completely inhibited by <50 nanomolar bafilomycin A(1), a specific vacuolar type ATPase inhibitor. The reconstituted H(+) pump was also inhibited by N,N'-dicyclohexylcarbodiimide or NO(3) (-) but not by azide or vanadate. Chloride stimulated both ATP hydrolysis by the purified ATPase and H(+) pumping by the reconstituted ATPase in the presence of K(+) and valinomycin. Hence, our results support the idea that the vacuolar H(+)-pumping ATPase from oat, unlike some animal vacuolar ATPases, could be regulated directly by cytoplasmic Cl(-) concentration. The purified and reconstituted H(+)-ATPase was composed of 10 polypeptides of 70, 60, 44, 42, 36, 32, 29, 16, 13, and 12 kilodaltons. These results demonstrate conclusively that the purified vacuolar ATPase is a functional electrogenic H(+) pump and that a set of 10 polypeptides is sufficient for coupled ATP hydrolysis and H(+) translocation.

Journal Article↗
PubMed1992

Persistent infection of rabbits with bovine immunodeficiency-like virus.

Chronic infection of rabbits was induced by a single intraperitoneal injection of bovine immunodeficiency-like virus (BIV)-infected cells. Ten BIV-infected animals were monitored serologically for up to 2 years. Results of serologic and virus rescue assays indicated that all animals became infected and demonstrated a rapid and sustained BIV-specific humoral response. BIV was rescued by cocultivation from spleen, lymph nodes, and peripheral blood leukocytes of infected animals. Viral DNA in immune tissues was confirmed by polymerase chain reaction amplification of BIV sequences. These data and specific immunohistochemical staining of mononuclear cells of the spleen for BIV antigen suggest that the infection is targeted to immune system cells.

Animals↗
PubMed1992

Tolerance and upregulation of acetylcholine receptors follow chronic infusion of d-tubocurarine.

The hypothesis that chronic competitive antagonism of nicotinic acetylcholine receptors (nAChR), even in the absence of immobilization or paralysis, induces proliferation of the receptor and tolerance to the competitive antagonist was tested. Chronic antagonism of the nAChR was achieved in rats by an infusion of d-tubocurarine (dTC) via subcutaneously placed osmotic pumps. After 2 wk of dTC or saline, the neuromuscular pharmacodynamics and nAChR number were examined. No differences in weight gain or mobility were observed between groups. Chronic dTC infusion at 2 wk resulted in a baseline concentration of 0.41 +/- 0.07 (SE) micrograms/ml, which, if achieved acutely, would cause a depression of the twitch tension to 60% of control twitch height. Moreover the experimental group was able to develop a baseline twitch tension of 50 g, similar to that of controls. Despite the baseline dTC concentration in the experimental group, the effective doses of dTC for twitch depression were similar to those of controls. The plasma dTC concentration required for steady-state twitch inhibition was significantly (P less than 0.05) higher in the experimental group (0.83 +/- 0.04 vs. 0.50 +/- 0.15 micrograms/ml) as were the extrajunctional nAChR (19.76 +/- 1.77 vs. 13.37 +/- 1.82 fmol/mg protein). The diaphragmatic nAChR were unaltered. This study confirms that chronic doses of dTC cause tolerance to its effects and proliferation of nAChR even in the absence of immobilization. The absence of nAChR changes in the diaphragm may be due to the higher margin of safety of the diaphragm for muscle relaxants than for peripheral muscles. Intensive Care Unit patients receiving chronic infusions of dTC to facilitate mechanical ventilation will require increased doses with time.

Animals↗
PubMed1992

Immunohistochemical evidence of high concentrations of metallothionein in pancreatic hepatocytes induced by cadmium in rats.

A recent study from our laboratory has shown that cadmium, a toxic heavy metal, is one of the most effective agents known for inducing hepatocytic transdifferentiation of the rat pancreas. With repeated injections of cadmium, the incidence of rats with pancreatic hepatocytic foci can be as high as 93%. Cadmium is also well known as a very potent inducer of metallothionein, a metal-binding protein that appears to be important in the biologic response to several toxic heavy metals in most tissues, including the pancreas. Therefore, the present study sought to determine if metallothionein was associated with cadmium-induced transdifferentiation of pancreatic cells. Expression of metallothionein was studied immunohistochemically by the peroxidase-antiperoxidase method in tissue sections of the pancreas of rats with pancreatic hepatocytes. High levels of metallothionein were localized primarily within the pancreatic hepatocytes. Surrounding normal pancreatic islet and acinar cells were not immunoreactive. Thus, metallothionein is expressed actively in cells transdifferentiated to hepatocytes by cadmium within the pancreas.

Animals↗
PubMed1992

Induction of tumours of the haematopoietic system by cadmium in rats.

Several of our recent studies in rats indicate an association between exposure to cadmium and haematopoietic tumours. In the first study, male WF rats received dietary cadmium (0-200 micrograms/g cadmium as cadmium chloride) for up to 77 weeks. A dose-related increase in large granular lymphocyte (LGL) leukaemia was observed with a maximal incidence in rats fed 100 micrograms/g cadmium. In a second study, male F344 rats received a single high dose of cadmium chloride (30 mumol/kg, s.c.) and were observed for 90 weeks. The high natural incidence of leukaemia in these rats (24%) was markedly reduced (6%) by this dose of cadmium. The paradoxical effects of cadmium on haematopoietic tumours may be the result of a dose-related spectrum of lymphotoxicity ranging from cell-specific cytotoxicity and carcinogenicity to destruction of key progenitor cell populations.

Animals↗
PubMed1992

Vimentin metaplasia in renal cortical tubules of preneoplastic, neoplastic, aging, and regenerative lesions of rats and humans.

Vimentin expression was studied immunohistochemically in renal cortical tubules of untreated male rats of various ages, rats exposed to toxins (barbital sodium, folic acid) and carcinogens (streptozotocin, N-bis(2-hydroxypropyl)nitrosamine, barbital sodium, and in humans of various ages with or without renal epithelial tumors. Fetal, neonatal, and young adult rats did not express vimentin in renal cortical tubules. Regenerative renal tubular lesions from rats with aging nephropathy and from rats with toxic nephropathy both expressed vimentin. Mitogenic lesions induced by folic acid at 24 hours, however, were not immunoreactive for vimentin. Carcinogen-induced preneoplastic renal cortical tubular lesions in rats were most often focally immunoreactive whereas strong vimentin expression was found in almost all induced renal tumors. In kidneys of three children (younger than 2 years of age), vimentin was not found in renal cortical tubular cells except in rare individual cells in one case. Vimentin was abundant in basophilic regenerative tubules in kidneys of aged individuals, however. Most (7/10) human renal carcinomas and latent preneoplastic or neoplastic renal tubular lesions found incidentally at autopsy (2/4) showed vimentin expression. The authors suggest that the switching to vimentin expression in phenotypically normal renal cortical tubular cells in rats and humans, which do not usually express the intermediate filament protein vimentin, should be considered vimentin metaplasia. Vimentin expression is dissociated from increased cell proliferation in hyperplastic and neoplastic lesions, however. Instead the degree of dedifferentiation of the tubule cells and changes in phenotype were associated with vimentin expression.

Age Factors↗
PubMed1991

Anticarcinogenic effects of cadmium in B6C3F1 mouse liver and lung.

The B6C3F1 mouse liver has been widely used for the evaluation of carcinogenic or tumor promoting efficacy of various organic compounds, although little is known about the actions of metallic carcinogens in this system. Thus, the ability of cadmium to initiate or promote tumors in B6C3F1 mouse liver was studied. In promotion studies, diethylnitrosamine (DEN; 90 mg/kg, ip) was given as an initiator to 5-week-old mice followed 2 weeks later by 500 or 1000 ppm of cadmium in drinking water for 50 weeks. DEN caused an elevation of liver tumor incidence (13 tumor bearing mice/45 total) over control (1/48) which was prevented by cadmium (DEN + 500 ppm cadmium, 3/42; DEN + 1000 cadmium, 0/47). Cadmium alone did not further reduce the very low spontaneous liver and lung tumor incidence at approximately 1 year of age. DEN-induced lung tumor incidence (15/45) was also reduced by cadmium (DEN + 500 ppm cadmium, 11/42; DEN + 1000 ppm cadmium, 1/47) to control levels (0/48). In initiation studies, cadmium (20 or 22.5 mumol/kg, sc) was given to 5-week-old mice (n = 30-60) 2 weeks before an established promoting regimen of sodium barbital (BB) in drinking water at 500 ppm level was begun. Barbital in drinking water was given continuously for up to 92 weeks. Such cadmium doses caused acute, focal hepatic necrosis. Mice treated with BB and killed at 97 weeks of age showed an elevation of liver tumor multiplicity (7.44 tumors/liver) over control (2.24) that was prevented by cadmium in a dose-related manner (20 mumol/kg cadmium + BB, 3.93; 22.5 mumol/kg cadmium + BB, 1.87). Cadmium alone given by injection also reduced spontaneous liver tumor multiplicity. These results indicate that cadmium inhibits tumor formation in the B6C3F1 mouse liver initiation/promotion system regardless of route of exposure or sequence of administration. The possibility exists that cadmium has a specific toxicity toward previously initiated cells within liver and lung.

Administration, Oral↗
PubMed1991

Prevention of nickel subsulfide carcinogenesis by local administration of Mycobacterium bovis antigen in male F344/NCr rats.

This study was designed to determine the effect of local inflammation on nickel subsulfide (Ni3S2) carcinogenesis. Male F344/NCr rats, 6-week-old, 20 rats/group, received a single i.m. injection of 2.5 mg of Ni3S2 alone or 2.5 mg of Ni3S2 mixed with either 0.5 mg of Mycobacterium bovis lyophilized cell walls (MB), 1 mg cortisol (CORT), or 1 mg indomethacin (IND). Two more groups of rats received i.m. Ni3S2 alone, as above, followed by a single s.c. dose of either 1 mg MB or 2 mg IND. The i.m. injections were made into the thigh muscles of both hind limbs; the s.c. injections were made at the neck area. The experiment was terminated at 71 weeks. The final yields of injection site sarcomas were 85% in the Ni3S2, 85% in the Ni3S2 + CORT, and 80% in the Ni3S2 + IND group. Only one injection site tumor (5%) was found in rats given i.m. Ni3S2 + MB. In contrast, the s.c. MB injection enhanced muscular carcinogenicity of Ni3S2 by shortening the latency and increasing the yield of tumors to 100% at week 39 (P less than 0.04 vs. Ni3S2 alone). The s.c. treatment with IND gave similar, though statistically nonsignificant results; 100% tumor yield was reached at week 42 (P less than 0.18 vs. Ni3S2 alone). Although local treatment with CORT or IND had no significant effect on the final tumor incidence by Ni3S2, it shortened the latency of tumors to 17 weeks compared with 23 weeks for Ni3S2 alone. MB, CORT, IND, or the injection vehicle (water) alone did not produce tumors. Local MB treatment had no significant effect on the retention of Ni3S2 at the injection site. The prevention of the Ni3S2 tumors by local MB might result from localization of numerous natural killer cells and macrophages and formation of giant cells observed at the injection site of Ni3S2, 1-14 days post injection. These cells could immobilize the carcinogen and destroy Ni3S2-transformed cells.

Animals↗
PubMed1991

Persistence of 5-bromo-2'-deoxyuridine in tissues of rats after exposure in early life.

Outbred L10 rats received 4 subcutaneous injections of 3.2 mg per rat 5-bromo-2'-deoxyuridine (BrdUrd) at 1, 3, 7 and 21 days of age. Groups of rats were sacrificed 1 h, 1 month or 49 weeks after the final injection. Tissues were fixed in 70% ethanol, embedded in paraffin and unstained sections were prepared for immunohistochemical demonstration of BrdUrd. A monoclonal antibody to BrdUrd was used with the avidin biotin peroxidase-complex (ABC) technique. The numbers of immunoreactive nuclei were tissue, cell and time-related. The labeling indices declined from 1 day to 49 weeks for all tissues studied. At 49 weeks after the last exposure to BrdUrd, many cells were still reactive, especially in tissues with normal low cell turnover (brain, uterine stroma). For cells with high turnover, including lymphocytes and ovarian germinative epithelium, few or no labeled cells remained at 49 weeks. This study provides clear evidence for the persistence of BrdUrd in normal tissues, some of which may be targets for the carcinogenic effect of the chemical and others which are not targets.

Animals↗
PubMed1991

Enhanced immunoreactivity of ras oncogene p21 protein in urinary bladder epithelium of rats treated with N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide.

Normal urothelium and various lesions of the rat urinary bladder induced by the dietary administration of 0.2% N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT) (up to 77 weeks) or by the combination of 0.2% FANFT and the subsequent administration of 5% sodium saccharin or 2% DL-tryptophan (up to 104 weeks) were evaluated for immunoreactivity with monoclonal antibody to ras p21 by avidin-biotin immunohistochemistry. Seventy-one to 100% of transitional cell carcinomas showed strong reactivity to the antibody to ras p21 depending on treatment with long-term administration of FANFT or by 6 weeks administration of FANFT followed by sodium saccharin or DL-tryptophan. Focal reactivity to the ras p21 antibody was frequently observed in the hyperplastic (57-96%) or normal appearing urinary bladder epithelium (50-100%) in rats treated with FANFT (FANFT alone or in combination with sodium saccharin or tryptophan) but not in hyperplasia or normal epithelium in rats given sodium saccharin or tryptophan alone, without pretreatment with FANFT or in untreated controls. The present results show that there is a close association of enhanced immunoreactivity with ras p21 antibody in the urinary bladder epithelium to FANFT treatment, and that ras p21 is expressed in normal, hyperplastic and neoplastic lesions of the bladder of rats treated with FANFT. These results suggest that enhanced immunoreactivity with ras p21 is observed as a consequence of the treatment with FANFT but it alone does not reflect the progression from benign to malignant lesions.

Animals↗
PubMed1991

Carcinogenicity study of fecapentaene-12 diacetate on skin painting in SENCAR mice.

To investigate the effects of both diol esterification and coadministration with antioxidant on the tumorigenicity of fecapentaene-12 (FP-12) preparations, diacetylfecapentaene-12 (DAFP-12) in dimethylsulfoxide (DMSO) was applied to SENCAR mouse skin with or without the stabilizer, vitamin E, twice/week for 5 weeks, following which all animals were promoted for up to 25 weeks by weekly applications of 12-O-tetradecanoylphorbol-13-acetate (TPA). While positive controls receiving 7,12-dimethylbenz[a]anthracene (DMBA) instead of DAFP-12 in a similar protocol all developed papillomas (average of 23/animal), papilloma incidence in mice given DAFP-12 did not differ significantly from that of the vehicle control. We conclude that DAFP-12 shows little or no tumor initiating activity for mouse skin even when coadministered with vitamin E.

Adult↗
PubMed1991

Chronic carcinogenic and toxic effects of a single subcutaneous dose of cadmium in the male Fischer rat.

The carcinogenic effects of cadmium have not been thoroughly assessed in the commonly used Fischer (F344) rat. This study determined tumor incidence in various tissues of male F344/NCr rats after a single dose of cadmium. Cadmium (as CdCl2) was given sc in the dorsal thoracic midline at 30 mumole/kg to 70 8-week old male F344 rats while controls (n = 50) received saline. Rats were observed during the next 90 weeks. Early deaths (less than or equal to 32 weeks), due mostly to acute cadmium-induced hepatotoxicity, accounted for 37 of the cadmium-treated rats while no control rats died in the same period. A high incidence of injection site sarcomas (ISS) occurred in the cadmium-treated group (21 ISS/32 rats at risk; 66%) while only 1/50 occurred in controls (2%). In fact, ISS were the major cause of morbidity after 35 weeks in cadmium-treated rats. These tumors were mostly fibrosarcomas, although histiocytic and osteogenic sarcomas also occurred. Testicular interstitial cell tumors, which show a very high spontaneous incidence in this strain (41/49; 84%), were not markedly affected by cadmium (30/31; 97%). This is in sharp contrast to other strains, such as the Wistar, in which cadmium treatment is reported to cause as much as an eightfold increase in interstitial cell (Leydig cell) tumor incidence. The incidence of large granular lymphocyte (LGL) leukemia, which also occurred frequently in control F344 rats (12/47; 26%) was markedly decreased (2/31; 7%) by cadmium. Our recent studies indicate acute lymphonecrotic effects occur with cadmium in lymphoid tissues of rats, and this may be related to the suppression of the leukemia. These results indicate that cadmium is very effective in inducing ISS in F344 rats, as is the case with other strains thus far tested, and also markedly reduces spontaneous leukemia incidence.

Animals↗
PubMed1991

Transplacental induction of mouse lung tumors: stage of fetal organogenesis in relation to frequency, morphology, size, and neoplastic progression of N-nitrosoethylurea-induced tumors.

Pregnant C3H/HeNCr MTV- mice were given a single intraperitoneal injection of 0.5 mmol N-nitrosoethylurea/kg on days 14, 16, or 18 of gestation. Six of the male offspring were sacrificed for study at the ages of 2, 4, 8, 16, 32, and 52 weeks. Grossly visible lung tumors were counted and all lungs were sectioned completely, saving every tenth section for histologic evaluation. All N-nitrosoethylurea-induced mouse lung tumors have previously been shown to originate from alveolar type II cells. Lung tumors were diagnosed as solid, papillary, or mixed solid/papillary types, and at the largest area of each tumor, the perimeter was measured and compared with the number of sections per tumor. The fraction of tumors detected grossly depended on size and, on average, only 51% of neoplasms present were detected macroscopically. A significant correlation was seen between the mean number of histological sections and perimeter length per tumor, in particular for small and medium sized papillary neoplasms. The growth of solid tumors was limited to a maximum size, after which they progressed towards papillary types. The numbers of transplacentally induced mouse lung tumors were distributed in direct proportion to the weight of the individual lung lobes, unrelated to day of treatment of type or tumor. Tumor biology depended on the day of treatment reflecting numbers of degree of differentiation of fetal alveolar type II cells, i.e., the target cell: most tumors developed in offspring treated on day 16, tumor size was greater and progression from solid to papillary neoplasms faster at earlier treatments, increase in tumor multiplicity postnatally was only seen in mice treated late in gestation, and mice treated on day 14 or day 16 showed a consistent ratio of solid to papillary tumors.

Animals↗
PubMed1991

Dose response of hepatic and renal DNA synthetic rates to continuous exposure of bromodeoxyuridine (BrdU) via slow-release pellets or osmotic minipumps in male B6C3F1 mice.

We studied the use of acute and chronic 5-bromo-2'-deoxyuridine (BrdU) administration for detection of DNA-synthesizing cells in the liver and kidney of B6C3F1 male mice. Six-week-old mice were exposed to BrdU either acutely with a single-pulse (IP) injection 1 hr before sacrifice or chronically with the use of slow-release pellets or osmotic minipumps at one of four BrdU dose rates. Pellets (2.5, 10, 25, and 50 mg) and minipumps (2.5 and 10 mg equivalents) were implanted subcutaneously on the backs of the animals 4 or 7 days before sacrifice). BrdU incorporation into DNA was determined by immunohistochemistry using an anti-BrdU antibody. Mice chronically exposed to BrdU demonstrated increased levels of nuclear labeling compared with those receiving a single-pulse injection. No time-related increases in nuclear labeling were detected in hepatocytes or renal tubule cells of mice exposed to BrdU pellets and in the kidneys of mice receiving BrdU minipumps at the 7-day compared with the 4-day time point. In some cases, the labeling indices at 7 days were significantly decreased compared with those at 4 days. In contrast, a time-related increase in nuclear labeling was seen in hepatocytes and Kupffer cells of mice exposed to BrdU minipumps. Therefore, the method used to administer BrdU chronically to the animal appears to play an important role in presenting the true proliferative scenario in cell kinetic studies. Our findings also provide evidence for an effect of BrdU on normal proliferation rates in these tissues.

Animals↗