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K P Keenan

Publications and source records attributed to K P Keenan.

At least 19 recordsLinked to original sources
PubMed2006

Assessing biofilm formation by Listeria monocytogenes strains.

When a microtitre plate assay was used to quantify biofilm production by Listeria monocytogenes strains following growth in Tryptone Soy Broth (TSB) for 48 h at 20 degrees C, 127 of 138 strains (92.0%) were classified as weak, 9 of 138 strains (6.5%) as moderate and only 2 of 138 strains (1.5%) as strong biofilm formers. The strains included environmental, animal, food (persistent and sporadic strains) and clinical isolates previously typed using esterase electrophoresis (ESE) and multi-locus enzyme electrophoresis (MEE). Strains from different sources produced similar quantities of biofilm, whereas biofilm production by ESE type II strains, irrespective of source, was greater than that observed for other ESE types. No correlation between MEE type and biofilm production was observed. A Petri dish assay which allowed parallel quantification and microscopic examination of biofilms was used to examine biofilm formation by selected L. monocytogenes strains during growth in TSB for 14 days at 20 degrees C. Results from these assays showed that following prolonged incubation, some L. monocytogenes strains categorized as weak biofilm formers by the 48 h microtitre assay, were able to form biofilms similar in terms of quantity and structure to those produced by strains classified as strong or medium biofilm formers. Results from 14-day Petri dish assays confirmed 48 h microtitre assays regarding greater biofilm production by ESE type II strains compared to other ESE types of L. monocytogenes. Biofilm production was similar for ESE type II persistent and sporadic food isolates but reduced for ESE type II clinical strains.

Bacterial Adhesion↗
PubMed2001

Caloric restriction mimetics: metabolic interventions.

Caloric restriction (CR) retards diseases and aging in laboratory rodents and is now being tested in nonhuman primates. One way to apply these findings to human health is to identify and test agents that may mimic critical actions of CR. Panel 2 focused on two outcomes of CR, reduction of oxidative stress and improved glucoregulation, for which candidate metabolic mimics exist. It was recommended that studies on oxidative stress should emphasize mitochondrial function and to test the efficacy of nitrone and other antioxidants in mimicking CR's effects. Studies should also focus on the long-term effects of compounds known to lower circulating glucose and insulin concentrations or to increase insulin sensitivity. Also, four other developing areas were identified: intermediary metabolism, response to infection, stress responses, and source of dietary fat. These areas are important because either they hold promise for the discovery of new mimetics or they need to be explored prior to initiation of CR trials in humans. Other recommendations were that transgenic approaches and adult-onset CR should be emphasized in future studies.

Animals↗
PubMed2000

The effects of diet, ad Libitum feeding, and moderate and severe dietary restriction on body weight, survival, clinical pathology parameters, and cause of death in control Sprague-Dawley rats.

A 2-year study was conducted in Sprague-Dawley rats to compare the effects of ad libitum (AL) feeding and dietary restriction (DR) on body weight, survival, cause of death, and clinical pathology parameters. Three groups of 120 rats/sex each received the following daily rations of a maintenance rodent diet: ad libitum (AL group); 75% of adult AL food consumption (25% DR group); and 45% of adult AL food consumption (55% DR group). Among the 3 groups, there were generally no differences in relative (food intake per gram of body weight) food consumption. Compared to the AL group, decreased body weight gain occurred in DR groups and was associated with an increase in survival proportional to the DR rate. The main cause of death was pituitary adenomas in all groups. Decreases in total leukocyte, segmented neutrophil, lymphocyte, and platelet counts occurred in the 55% DR group. In serum biochemistry, there were decreases in total protein, albumin, total and HDL cholesterol, and total calcium, and increases in alkaline phosphatase activities and chloride in 55% DR females, as well as decreases in triglycerides in the 55% DR group and in 25% DR females. Results of urinalyses showed decreases in urine volume and protein, and increases in urinary pH in both DR groups. In conclusion, a DR rate of approximately 25% appears to be appropriate for Sprague-Dawley rats in toxicity and carcinogenicity assays to improve survival without impairing growth and routine clinical pathology parameters.

Animals↗
PubMed1999

Diet, caloric restriction, and the rodent bioassay.

The diet can significantly alter the results of toxicity and carcinogenicity studies. Ad libitum (AL) overfeeding of excessive calories to sedentary adult rodents is one of the most poorly controlled variables affecting the current rodent bioassay. AL-overfed rodents develop an early onset of adverse metabolic events, endocrine-disruptive degenerative diseases, and tumors that result in early morbidity and mortality. AL food consumption is extremely variable, but has a strong correlation with adult body weight, obesity, and survival. AL feeding of diets with modified protein, fiber, and energy content are not as effective as simple, moderate dietary (caloric) restriction (DR) in controlling these study variables. Moderate DR (70-75% of adult AL) is operationally simple and controls adult body weights, prevents obesity, and improves health and survival by reducing or delaying diet-related endocrine, renal, and cardiac diseases. Moderate DR provides a uniform rodent model, increases treatment exposure time, and increases the statistical sensitivity of these chronic bioassays to detect true treatment effects. Feeding a balanced diet by a moderate DR regimen of 70-75% of the maximum, unrestricted adult AL food intake is recommended for conducting well-controlled toxicity and carcinogenicity studies.

Animals↗
PubMed1998

Morphological and hormonal changes in the ventral and dorsolateral prostatic lobes of rats treated with finasteride, a 5-alpha reductase inhibitor.

BACKGROUND: In rats, the prostate is divided into three distinct lobes, and the lobes are dependent on androgens [testosterone (T) and dihydrotestosterone (DHT)] as trophic hormones. However, the reasons for the difference in the incidence of proliferative changes reported are not well-understood. Administration of finasteride, a 5-alpha reductase (5alphaR) inhibitor which selectively inhibits the conversion of T to DHT, results in elevated intraprostatic T levels. However, long-term (2 years) administration of finasteride results in no increase in proliferative changes in the ventral lobes of the rat prostate. Therefore, studies were designed to determine the differences in intraprostatic hormonal levels, morphology, and 5alphaR activity in different lobes of the rat prostate. METHODS: Sexually mature male Sprague-Dawley rats were used in all studies. Finasteride was administered orally to rats. The methodology included determination of intraprostatic T and DHT levels by radioimmunoassay, qualitative and quantitative evaluation of prostatic morphology, and in vitro determination of 5alphaR activities in rat prostatic lobes. RESULTS: A significant amount of 5alphaR activity was observed in the dorsal, ventral, and lateral lobes of the rat prostate. Both 5alphaR isozymes (types 1 and 2) were present in all lobes, based on 5alphaR activities observed at both acidic and neutral pH. Oral administration of finasteride (160 mg/kg/day) for 15 days resulted in significant (P < or = 0.001) decreases in intraprostatic DHT levels and increases in T levels; when compared to controls, the mean decrease in DHT levels in the ventral and the dorsolateral lobes was 86% and 94%, respectively, and the mean increase in T levels in the ventral and the dorsolateral lobes was approximately 3 times and 20 times, respectively, higher than in controls. Chronic administration of finasteride (80 mg/kg/day) for 6 months resulted in significant (P < or = 0.001) decreases in the weights of the prostatic lobes, which correlated with significant (P < or = 0.001) decreases in the total number of epithelial and stromal cells per gland in both the ventral and dorsolateral lobes of the prostate. There were no qualitative differences in prostatic morphology between the control and finasteride-treated groups. A short-term study in control rats exposed to bromodeoxyuridine (Brdu) showed that the number of Brdu-labeled cells in the dorsolateral lobe was significantly (P < or = 0.05) greater than in the ventral lobe. CONCLUSIONS: This first comparative study has highlighted some of the similarities and differences among the prostatic lobes of the rat. Inhibition of conversion of T to DHT with finasteride resulted in a significant increase in intraprostatic T levels and a significant decrease in DHT levels in rats; despite a significant increase in intraprostatic T levels, the prostate remained atrophic, indicating that DHT alone has a trophic effect on the prostate.

Animals↗
PubMed1997

Effect of early body weight and moderate dietary restriction on the survival of the Sprague-Dawley rat.

The effects of ad libitum (AL) feeding, moderate dietary restriction (DR), and initial (6-week) and one-year body weights on the two-year survival of the Sprague-Dawley (SD) rat were evaluated. DR-fed rats were given approximately 75 percent of the adult AL food intake. At two years, body weights of DR-fed males and females were approximately 69 and 58 percent of the AL-fed male and female body weights, respectively. The 2-year survival rate was 80 and 74 percent in DR-fed males and females, respectively, and 28 and 38 percent in AL-fed males and females, respectively. This increase in longevity indicates that DR-fed males and females in carcinogenicity studies would have 14.8 and 9.1 additional weeks of exposure in a 2-year period to test compounds, respectively, compared to AL-fed animals. There was no correlation between initial body weight and 2-year survival in DR or AL-fed rats. There was no association between 1-year body weight and 2-year survival among DR-fed rats. However, AL-fed rats with the greatest 1-year body weight had a lower 2-year average survival compared with the lightest AL-fed rats; this trend was statistically significant only in males. Body weights between the first and second years were statistically significantly correlated for both genders and feeding regimens but no correlation was observed between pretest and 2-year body weights. These findings demonstrate that initial body weight is not the determining factor of 2-year survival, but that the total adult food (caloric) intake is important. In conclusion, moderate dietary restriction prevented excessive body weight gain and greatly increased the 2-year survival of the SD rat. Initial body weights did not correlate to 2-year body weight gain and were not a predictive biomarker of 2-year SD rat survival.

Animals↗
PubMed1997

The effects of diet, overfeeding and moderate dietary restriction on Sprague-Dawley rat survival, disease and toxicology.

Overfeeding by ad libitum (AL) food consumption is the most significant, uncontrolled variable affecting the outcome of the current rodent bioassay. The correlation of food consumption, the resultant adult body weight and the 2-y survival in Sprague-Dawley rats is highly significant. Feeding natural ingredient diets that varied in protein, fiber and metabolizable energy content did not improve low 2-y survival if Sprague-Dawley rats were allowed AL food consumption. Moderate dietary restriction (DR) of all diets tested significantly improved survival and delayed the onset of spontaneous degenerative disease (i.e., nephropathy and cardiomyopathy) and diet-related tumors. By 2 y, moderate DR resulted in an incidence of spontaneous tumors similar to that seen with AL consumption; however, the tumors were more likely to be incidental and did not result in early mortality. There was a decreased age-adjusted incidence in pituitary and mammary gland tumors, but tumor volume and growth time were similar in the AL and DR groups, indicating a similar tumor progression with a delay in tumor onset. Moderate DR did not significantly alter drug-metabolizing enzyme activities or the toxicologic response to five pharmaceuticals tested at maximum tolerated doses (MTD). However, moderate DR did require higher doses of compounds to be given before classical MTD were produced with four pharmaceutical drug candidates. Toxicokinetic studies of two of these compounds demonstrated steady-state systemic exposures that were equal or higher in moderate DR-fed rats. These and other data indicate that moderate DR is the most appropriate method of dietary control for rodent bioassays used to assess human safety of candidate pharmaceuticals.

Animals↗
PubMed1996

The effects of overfeeding and moderate dietary restriction on Sprague-Dawley rat survival, pathology, carcinogenicity, and the toxicity of pharmaceutical agents.

Ad libitum (AL) overfeeding is the most significant uncontrolled variable effecting the rodent bioassay. There is a highly significant correlation between food consumption, the resultant body weight, and two-year survival in laboratory rats. We have studied the effects of AL overfeeding, moderate dietary restriction (DR) and several modified diets on Sprague-Dawley (SD) rat longevity, spontaneous disease, carcinogenesis and the toxicity of pharmaceuticals. AL feeding of diets varying in protein, fiber and metabolizable energy content did not significantly alter two-year rat survival. Moderate DR (within the range of reported AL food intake) of all diets tested significantly improved survival and delayed the onset of spontaneous degenerative disease and diet-related tumors compared to AL-fed rats. Moderate DR resulted in a similar incidence of spontaneous tumors by 2 years, however, the tumors were more likely to be incidental and not result in early mortality. There was a decreased, age-adjusted incidence of pituitary and mammary gland tumors, but tumor volume and growth time was similar between AL and DR groups indicating similar tumor progression with a delay in tumor onset. Moderate DR did not change Phase I and Phase II drug metabolizing enzyme levels and did not significantly alter the toxicological response to 5 pharmaceuticals tested at maximum tolerated doses (MTDs). Additional studies with 4 pharmaceutical candidates did demonstrate that moderate DR allowed higher doses of compounds to be given before classical MTDs were observed. However, toxicokinetic studies of two of these compounds demonstrated steady state systemic exposures that were either equal of higher in the moderate DR fed rats. These and other data indicate that the moderate DR fed SD rat is a more appropriately controlled rodent model for toxicity and carcinogenicity studies to assess human safety of candidate pharmaceuticals.

Animals↗
PubMed1994

Qualitative and quantitative evaluation of prostatic histomorphology in rats following chronic treatment with finasteride, a 5-alpha reductase inhibitor.

OBJECTIVE: To determine any potential direct and/or indirect effects of elevated intraprostatic T levels on the prostates of rats chronically (1-2 years) exposed to high doses (160 mg/kg/day) of finasteride, a selective inhibitor of 5-alpha reductase. METHODS: Sprague-Dawley male rats were administered daily finasteride by oral gavage. Prostates from all rats were weighed, fixed in 10% neutral buffered formalin, and processed for light microscopic examination. The volume fractions of the prostatic glandular and stromal compartments were quantitated by morphometric analysis. RESULTS: Administration of finasteride at doses of 20, 40, and 80 mg/kg/day for one year resulted in a significant (P < or = 0.05) decrease in prostatic weight; prostatic atrophy was evident by light microscopy. Morphometric analysis of the prostate showed that chronic finasteride administration resulted in a significant (P < or = 0.001) decrease in the absolute volume of both glandular (-65.2%) and stromal (-57.1%) compartments of the prostate. Furthermore, the total number of epithelial and stromal cells per gland were significantly (P < or = 0.002) decreased in finasteride-treated rats compared with vehicle controls; the magnitude of mean decrease was 69.8 percent and 50.6 percent of controls in epithelial and stromal cells, respectively. In addition, prostates from all two hundred fifty rats in a two-year study were qualitatively evaluated by light microscopy. Administration of finasteride at doses ranging from 2.5 mg/kg/day to 160 mg/kg/day for two years did not result in an increase over the background incidence of prostatic focal hyperplasia or adenoma. No malignant tumors of the prostate were seen in any of the groups. CONCLUSIONS: These studies have demonstrated that the expected pharmacologic effects of finasteride on the prostate are maintained following chronic treatment and that there was no evidence of a direct and/or an indirect effect of elevated intraprostatic T on prostatic morphology in rats.

5-alpha Reductase Inhibitors↗
PubMed1994

Juxtaglomerular cell hypertrophy and hyperplasia induced in rhesus monkeys by angiotensin II receptor antagonists.

BACKGROUND: Juxtaglomerular (JG) cell hypertrophy and hyperplasia were investigated in rhesus monkeys given angiotensin II (AII) AT1 receptor antagonists L-158,338 and DUP 753 (MK-0954, losartan). EXPERIMENTAL DESIGN: In 2 initial studies, L-158,338 was given orally at 10, 30, and 90 mg/kg/day for 3 or 14 weeks. To investigate the observed JG hypertrophy and hyperplasia, in a third 5-week experiment L-158,338 was given alone at 90 mg/kg/day, or with physiologic saline supplementation at 25 ml/kg/day, or coadministered with the angiotensin converting enzyme inhibitor enalapril at 10 mg/kg/day. Physiologic saline was given to attempt to suppress renin release through volume expansion and/or sodium retention. Enalapril was given to lower plasma AII levels and observe whether JG cell hypertrophy and hyperplasia were increased or decreased. For comparison, DUP 753 was given at 90 and 300 mg/kg/day. Plasma renin activity and AII concentration were measured in this study. RESULTS: Dose- and time-dependent increases in JG cell hypertrophy and hyperplasia were seen in the 2 initial experiment. In the third experiment, plasma renin activity and AII concentration were increased 3-fold and 6-fold over pretest values by L-158,338 at 90 mg/kg/day for 5 weeks. Saline supplementation had no effect on these parameters but diminished the group mean severity grade for JG hypertrophy and hyperplasia from 1.5 to 1.0. Enalapril coadministration had no effect on plasma renin activity, whereas it blunted the plasma AII increase caused by L-158,338 and increased the group mean grade to 2.5. DUP 753 at 300 mg/kg/day produced similar increases in plasma renin activity and AII concentration but only resulted in grade 1 JG cell hypertrophy and hyperplasia. CONCLUSIONS: L-158,338-induced JG cell hypertrophy and hyperplasia is an exaggerated pharmacologic response that can be modulated by saline supplementation and angiotensin converting enzyme inhibition. These results suggest that decreased renal perfusion or altered sodium homeostasis and plasma AII concentration are important variables that contribute to AT1 receptor blockade to induce JG cell hypertrophy and hyperplasia.

Angiotensin II↗
PubMed1993

Cytotoxicity as measured by trypan blue as a potentially confounding variable in the in vitro alkaline elution/rat hepatocyte assay.

Rat hepatocytes treated in vitro with A2RA, an angiotensin II receptor antagonist, displayed an increased level of DNA-strand breaks as determined by alkaline elution, without an appreciable increase in cytotoxicity as determined by a trypan blue dye exclusion assay at harvest. The alkaline elution profile appeared to have two components: a rapidly eluting component detected in the first fraction collected (often associated with DNA from dead or dying cells), followed by a more slowly eluting component detected in the subsequent fractions. Further analysis of hepatocytes treated with A2RA by pulsed-field gel electrophoresis and neutral elution revealed significant levels of DNA double-strand breaks. Electron microscopy (EM) showed pronounced damage to mitochondria; although cell blebbing was seen using both EM and light microscopy, the plasma and nuclear membranes appeared intact when examined by EM. Cellular ATP levels decreased precipitously with increasing doses of A2RA, falling to less than 10% of control values at a dose of 0.213 mM A2RA, a concentration showing 100% relative viability by trypan blue at harvest. Thus, whereas in our experience trypan blue dye exclusion accurately reflects cytotoxicity induced by the majority of test agents, in this rather unusual case, trypan blue did not accurately reflect compound-induced cytotoxicity at harvest since there was no concurrent loss of membrane integrity. However, when hepatocytes treated with A2RA were incubated for either 3 h or 20 h in the absence of compound, a sharp, dose-dependent decline in viability was observed using trypan blue dye exclusion. Together with the initial, dose-dependent drop in the alkaline elution curve, these data suggest that the observed DNA double-strand breaks arose as a consequence of endonucleolytic DNA degradation associated with cytotoxicity, rather than by a direct compound-DNA interaction. Since DNA double-strand breaks behave under alkaline denaturing conditions as two single-strand breaks and can therefore produce increases in the alkaline-elution slope values, a necessary criteria for a valid positive result in this assay is that cytotoxicity by trypan blue dye exclusion will not be greater than 30%. Our data, however, indicate that interpretation of the elution assay as a test for genotoxicity can still be confounded by the failure of the trypan blue dye exclusion assay to reflect cytotoxicity in the unusual instance when there is no concurrent, immediate loss of membrane integrity.

Angiotensin Receptor Antagonists↗
PubMed1992

Induction of emphysema and bronchial mucus cell hyperplasia by intratracheal instillation of lipopolysaccharide in the hamster.

The aim of this study was to determine whether lipopolysaccharide-induced elastase release from recruited neutrophils in the hamster lung would induce emphysema, measured by mean linear intercept (Lm) and bronchial mucus cell hyperplasia (BMCH), scored in tissue sections stained with periodic acid-Schiff. Lipopolysaccharide (LPS) was instilled transorally twice a week for up to 5 weeks in hamsters. At 4 weeks after seven LPS instillations, Lm amounted to 87.6 +/- 1.2 microns, while it was 68.3 +/- 1.5 microns after seven saline instillations (P less than 0.01). At 6 months after the sixth LPS instillation, the Lm of these lungs was 83.3 +/- 1.6 microns, indicating irreversible tissue destruction. LPS-treated hamsters showed marked to severe BMCH, which was most evident in large intrapulmonary airways. Instillations of highly selective inhibitor of hamster PMN elastase resulted in 50 per cent inhibition of LPS-induced emphysema. The development of BMCH was inhibited by approximately 35 per cent by this agent. To study the response in time of cellular infiltration after a single LPS instillation, the lungs of groups of four hamsters were lavaged at different time points. PMN recruitment showed peak values at 4 and 48 h after LPS instillation and returned to baseline values at 96 h. Simultaneous intratracheal instillation of LPS and anti-TNF alpha antiserum resulted in a considerable reduction of neutrophil influx into bronchoalveolar spaces in the first 6 h after instillation.

Animals↗
PubMed1992

Studies of early hepatocellular proliferation and peroxisomal proliferation in Sprague-Dawley rats treated with tumorigenic doses of clofibrate.

Clofibrate, a peroxisome proliferator, is hepatocarcinogenic in rats in a dose-dependent fashion. While there is a relationship between peroxisome proliferation and rodent liver carcinogenesis, recent evidence also suggests an association between the tumorigenicity of peroxisome proliferators and sustained cell proliferation. To investigate the role of early cell proliferation in clofibrate-induced carcinogenesis and the predictive potential of this endpoint, in a 3-month study, rats were fed clofibrate doses equivalent to those used in the chronic bioassay, and cell proliferation was determined after 1 week and 3 months, using a 1-week continuous bromodeoxyuridine (BrdU)-labeling technique. Adult Sprague-Dawley rats were fed clofibrate at 1500, 4500, or 9000 ppm. Six rats/sex/group were killed after 1 or 13 weeks of treatment. Osmotic minipumps containing BrdU were implanted into rats 7 days prior to necropsy to determine the cumulative 7-day hepatocyte labeling index immunohistochemically. A dose-related increase in hepatocyte labeling index was seen after 1 week of treatment. However, at 13 weeks, sustained increases in hepatocyte proliferation were not seen; but a dose-related decrease in the hepatocyte labeling index was observed. Liver stereology at 13 weeks demonstrated a dose-related increase in liver weight and volume, but a decrease in hepatocyte nuclei per unit volume, a minimal increase or no change in the total number of hepatocyte nuclei per liver, and an absolute decline in the total number of BrdU-labeled hepatocyte nuclei per liver. These data suggest that in rats, clofibrate may influence hepatocarcinogenicity by decreases in normal hepatocyte proliferation over time and this effect may influence the pathogenesis of tumors at time points beyond 13 weeks of treatment.

Administration, Oral↗
PubMed1992

Enantioselective induction of peroxisomal proliferation in CD-1 mice by leukotriene antagonists.

The effects of a racemic leukotriene antagonist (MK-0571) and its component enantiomers (L-668,018 and L-668,019) on hepatic peroxisome proliferation were examined in mice, rats, and rhesus monkeys. Administration of racemic MK-0571 to mice resulted in increased liver weights, increased peroxisomal volume density, and a pleiotropic induction of characteristic peroxisomal and nonperoxisomal enzyme activities associated with peroxisomal proliferation. When the individual enantiomers of MK-0571 were administered to mice, a pronounced enantioselective induction of peroxisome proliferation was observed. Toxicokinetic studies showed that the levels of each enantiomer in the liver or plasma after separate administration were similar. Thus, the enantioselectivity in the induction of peroxisome proliferation could not be explained on the basis of pharmacokinetic differences between the enantiomers. The hepatic peroxisomal response of the rat to MK-0571 was greatly attenuated compared to the mouse. As has been seen with other peroxisome-proliferating agents, MK-0571 had no effect on either peroxisomal volume density or peroxisomal enzyme activity in monkeys. Due to the high degree of enantiomeric discrimination toward the induction of peroxisomal proliferation by these enantiomers, compounds of this type may prove useful as probes to examine the mechanisms by which peroxisomal proliferating agents induce their effects.

Animals↗
PubMed1991

Cell-to-cell communication: a differential response to TGF-beta in normal and transformed (BEAS-2B) human bronchial epithelial cells.

The effects of transforming growth factor beta (TGF-beta) on cell-to-cell communication were investigated in the log phase of growth in normal BE and in adenovirus-12 SV40 hybrid virus transformed BE cells (strain BEAS-2B). Gap junctions in these cells were identified immunocytochemically. Exposure of BE cells to exogenous TGF-beta (0.04-4.0 pM) in serum-free keratinocyte growth medium (KGM) for 1 or 24 h reduced the rate of fluorescent dye transfer (i.e. cell-to-cell communication) by 30-50% in BE cells. Inversely, in BEAS-2B cells, TGF-beta after 1 h induced a 2- to 10-fold increase in the rate of dye transfer. After 24 h of TGF-beta, communication among BEAS-2B cells was not significantly different from controls (no exogenous TGF-beta). The protein kinase C (PKC) inhibitor H-7 induced a dose-dependent enhancement in communication, which was even higher in the presence of TGF-beta (4 pM X 24 h). The calmodulin antagonist W-7 enhanced communication in BEAS-2B cells independently of the presence of TGF-beta. In keratinocyte basal medium (KBM) supplemented with EGF (5 ng/ml) or with TGF-beta (4.0 pM) dye transfer was reduced or enhanced respectively. The combination of EGF and TGF-beta in KBM antagonized the stimulatory effect of the latter on communication in BEAS-2B cells. In BE cells, continuous exposure (4 days) to TGF-beta in KGM induced a dose-dependent inhibition of proliferation and an increased expression of a keratinized, epidermoid phenotype. This correlated with a reduction in the expression of a mucous secretory phenotype. Increased exposure to TGF-beta (0.04-4.0 pM) decreased the labeling index in BEAS-2B cells, but the cells retained a growth advantage over normal BE cells, and did not express a keratinized epidermoid morphology. With respect to dye transfer as an index of cell-to-cell communication, we conclude (i) that an inhibition or enhancement of communication is involved in the response of bronchial epithelial cells to mitogens (e.g. epidermal growth factor) or growth inhibitors (e.g. TGF-beta), (ii) that PKC and Ca(2+)-calmodulin-dependent processes regulate dye transfer, and (iii) the effects of TGF-beta are mediated by PKC.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1989

Morphological and cytokinetic responses of hamster airways to intralaryngeal or intratracheal cannulation with instillation of saline or ferric oxide particles in saline.

The morphological and proliferative effects of intratracheal cannulation (ITC) or intralaryngeal cannulation (ILC), with or without the instillation of saline or Fe2O3 particles in saline, were studied in Syrian golden hamsters. Instillation of Fe2O3 in saline at either airway level resulted in a similar distribution of Fe2O3 particles in all lung lobes. ILC produced laryngeal mucosal wounds. ITC produced laryngeal and tracheal mucosal wounds. The cannula-induced wounds were associated with proliferative epithelial lesions. ITC, but not ILC, resulted in significant increases in the mitotic rates (MR, 6-h colchicine blockade) of tracheal epithelial cells at 24 and 32 h postcannulation. Instillation of saline by ITC produced slight increases in intrapulmonary bronchial and bronchiolar MR, but saline given by ILC did not increase MR at any airway level. Instillation of Fe2O3 particles in saline by ITC produced increases in tracheal, intrapulmonary bronchial, and bronchiolar MR. Instillation of Fe2O3 particles in saline by ILC had little effect on tracheal MR, but increased intrapulmonary bronchial and bronchiolar MR. Foci of Fe2O3 particle-laden macrophages were associated with mild bronchiolar-alveolar hyperplasia at the junctions of the terminal bronchioles and the alveolar ducts. The cytokinetic and morphological changes in the intrapulmonary airways were associated with the influx of inflammatory cells in response to Fe2O3 particle deposition. The marked increases in tracheal MR and the localized hyperplastic tracheal epithelial lesions were clearly associated with mechanical wounding from the cannula during ITC. Comparative studies using ILC or ITC instillation techniques allowed further investigations of the important role of tracheal mucosal wounding in the induction of respiratory carcinogenesis, as described in a companion paper (Keenan et al., Cancer Res., 49: 1528-1540, 1989).

Animals↗